I did some reasearch on gnomes in other settings, and while Races of Stone wasn't helpful at all (stupid chilklike prankster-illusionists), the older Complete Book of Gnomes & Halflings was very much so.
And I got lots of ideas how their biology and the prestablished facts of their culture would determine their society.

Gnomes are one of the major humanoid races that inhabit the Barbarian Lands. While they are both short in stature and small in numbers, they play a comparatively major role in the affairs of the taller people.

Physical Description
Gnomes have similar statures to humans and elves but stand noticeably shorter at less than four feet. With their round faces and thick noses, their heads appear proportionally bigger in relation to their body, and they are usually somewhat stout and broad shouldered in stature, which clearly makes them stand apart from human children. Gnomes have light brown skin in shades of earth or clay, brown or gray eyes, and brown hair, while males grow short beards. Like elves, gnomes have slightly pointed ears, but this is usually much less pronounced and less notable.

Despite their small size and lack of physical strength, gnomes possess a remarkable endurance and resilience towards exertions. Gnomes can walk or work in mines for hours without breaks and possess phenomenal resistance to disease and poison and even can tolerate the corruption of Taint much better than almost anyone else. The toughness of gnomes rivals that of the kaas, which are several times their size and more than twice as tall.

And addition, gnomes are also very long living and surpassed in that only by elves. Gnomes are generally considered to be adults in their early thirties and can live well over two centuries. Unlike elves however, gnomes age visibly throughout their whole lives and are much more similar to humans in that regard.

Like elves and lizardfolk, gnomes have been living in the Barbarian Lands for a very long time. However, very few is known about their early history before the Age of the Clans. Gnomes have always been most at home in hills and mountains, especially the Border Hills, the Mountains of the Upper River Valley, and the Mountains on the northern edge of the Southern Clanlands, where the majority of their present settlements are located. There are only a few gnomish clans living in the foothills of the Northlands, which always have been especially secluded.

Relations between gnomes and the other humanoid races have increased significantly since the dawn of the Age of Kings, when elven merchants showed an immense demand for gnomish steel weapons and quality steel ingots, which had a major effect on elven clan politics.

Culture and Society
Even when compared to humans, gnomes live in very densely packed communities of large inter-related families. Gnome houses are often home to one to two dozen people.

In gnomish society, gender roles are quite similar to those of humans. Fieldwork and hunting is mostly the domain of men, while women have almost complete control over the homes. Business is one of the fields of gnomish society where men and women are roughly equally involved as it is related to both the male and female sphere of responsibilities, though finances and bookkeeping are generally regarded as female skills. Gnomes do have a concept of nobility, but it includes few legal privileges and is more an aspect of social standing, which is mostly determined by wealth and success of certain families. In larger towns, they do form a patrician elite that holds the most political and economic power.

Gnomes are perfectly aware of the fact that they are the smallest and physically weakest of the humanoid races, which greatly influence how they interact with people of other races and face the outside world. Generally, gnomes try to avoid open confrontation as much as possible as there are few situations in which they could easily overpower their opponents. Instead appeasing the other side is usually their first course of action. While they do have their pride, most gnomes are quite willing to accept temporary humiliations instead of being drawn into a fight with unfavorable odds. Seeing this as a sign of weakness or gnomes being pushovers can prove to be quite dangerous however. When a direct, and potentially lethal confrontation seems inevitable, gnomes will often concede defeat and initially give in to the demands of their opponents. Which particularly larger and stronger opponents are often much too willing to take at face value. When armed fighting breaks out, fast but ordered retreat is often the first priority. However, it is a mistake to believe that gnomes are easily defeated as they will often use that opportunity to prepare for the next confrontation in which they will have the odds decisively in their favor. Only if everything is in place will gnomes strike back, with very underhanded business practices, ambushes, or even outright assassination, after their enemies thought them defeated and themselves in safety. This has given gnomes a reputation of being liars or cheats, as they will often make promises they have no intention to keep, to get themselves out of tight spots.

Life in gnome burrows is very cramped with lots of people living living tightly packed together. Politeness and respect for personal privacy have an extremely high value in gnome society to compensate for that. Provocations and insults are frowned upon greatly and while gnomes can show great restraint to not respond to them in kind, it significantly affects the respect gnomes have for other people and their willingness to compromise or provide help. People who unnecessarily aggravate arguments and disagreements will fiend very few friends among gnomes, but if their enemies are willing to do the same, gnomes are generally trying their best to remain civil and find mutually acceptable compromises. Life in the communal areas of gnome burrows is often loud and crowded with everyone trying to take part in the cheerful spirit. As most gnomes see it, bad mood and anger can easily be pushed aside for a few hours just by being willing to go with the flow. With the living condition in gnome settlements, one has to learn to swallow personal pride and restrain oneself from being rude to others who are getting bothersome. As a compensation, private quarters, which are often very small and belonging to no more than one to three gnomes, are absolutely forbidden places for everyone else. Only when offered may anyone enter the private room of a gnome, and even asking for permission is a serious taboo. Secretly entering, or even forcibly intruding into the private rooms of others is a very severe crime and an almost irrevocable breach of trust. Because gnome settlements have few open spaces, gnomes may appear as quite bold in how they show up at other peoples homes and expect immediate entrance, but they are usually very reluctant to enter sleeping quarters and private studies. And while some might go as far as helping themselves at food and drink, only the most unscrupulous would even touch any personal items of other people or search through bags and backpacks of others.

An aspect of gnome society, that is often quite hard for outsiders to comprehend, is the often very dry type of gnome humor. With personal restraint being an important gnomish virtue and direct accusations and outbursts of negative emotions being frowned upon, irony and the parody of politeness play a great part in gnome humor. Affected anger and offense, which are of course restrained as proper etiquette demands, is part of most well meant jokes gnomes frequently play on each other, but the subtle clues by which gnomes are told they just had been duped are almost always missed by outsiders. Gnomes may appear slightly unhinged, erratic, or outright abusive to others, while they only intend to make lighthearted jokes. To gnomes, making constant jokes about pent up aggressions, is one of the best ways to keep tension from arising and also regarded as a safe way to give others hints that they are getting close to overstepping boundaries.

Gnome villages often consists only of a few houses, which are mostly located underground. On the surface, villages consists mostly of barns, stables, and some workshops that produce a lot of smoke and fumes, while living quarters are mostly below ground. Only the main gates of most gnome homes are visible on the surface, which lead to an entrance hall from which tunnels and staircases lead down to the majority of rooms. It is not uncommon that villages and towns also have large communal spaces underground, which are connected to the homes by tunnels that serve as underground streets. Unlike real underground living races, gnomes spend a great deal of time outside on the surface where they tend to their fields and herds. Only during winter does public life move almost entirely underground with many gnomes not taking a step outside for weeks.

Most gnomes take their crafts and professions very seriously. In the high buzz activity of gnome homes and villages, concentrating on ones work is a highly valued distraction and it is considered very impolite to disturb other peoples work. Workshops and kitchen are often used by many people, but most gnomes learn very early in their lives to tone out the drone and chatter that is occurring right behind their backs.

Gnome craftsmanship is often sturdy and simple, made from solid and durable materials and eschewing delicate details for more stylized shapes. Since gnomes are well at home underground, they are also the greatest and most experienced miners anywhere in the Barbarian Land. Their most well known and most appreciated handiwork are the arts of metalworking. While gnomish smiths and craftsmen also work very well with bronze, silver, and gold, it is the steel produced in Komkaren foundries that is their most prized, and most valuable industry. However, their craftsmanship in forging weapons and armor is also among the best and frequently surpasses the work of the most talented elven smiths. Masterwork weapons and armor are almost always made from gnomish steel and most suits of heavy armor found among any of the humanoid races has been made by gnomish armor-smiths.

There are two main divisions of Gnomes in the Barbarian Lands, called the Komkaren and the Hoyaren, which very roughly mean "mountain people" and "forest people".

The Hayoren are the smaller of the two gnomish tribes and found mostly in the Southern Clanlands. Most Hayoren live in the southern Parts of the Great Forest, but there are also some Hayoren towns in the mountains near the coast.

The Komkaren are found mostly in the western regions of the Barbarian Lands, centered on the Border Hills. The Komkaren are widely known throughout the lands as the greatest miners and metalworkers and still basically hold a monopoly on the production of high quality steel that is highly valued among the other races.

The gnomes of the Lands of the Barbarian Kings share traits of dwarves, gnomes, and halflings and have their own set of racial traits for player characters and NPCs.

While it may seem a bit convoluted, gnome humor is not made up but straight from my home. Even people in the rest of Germany regard us as grumpy and humor-less and are suprised to hear it explained. Not to speak of the japanese people I talked to, who speak perfect german.

Here is a question for all of you. Do you like to have all descriptions here in the thread, or is it just the same to you if I only post links to the new pages of the archive? It isn't really that much extra work for me, but might get quite outdated in the future, as I won't update older posts.