Being fond of ponies, I'd like to join in, assuming you don't mind. My first planned character is below, so please let me know what you think.
Turns out a lovable rogue filly fits in better than I expected!
Name: Night Jewel
Appearance: A young unicorn filly with a purple coat, a long, flowing, pale blue mane and tail, blue eyes and a toolkit cutie mark.
Skills: Manipulation of mechanisms. Her magic can make small alterations to the inner workings of mechanical devices, whether to sabotage or repair them.
Biography: Night Jewel has been a wanderer for most of her life, living by her wits and her nimbleness. She rarely stays in one place for very long due to her tendency to get into trouble. Not even she knows much about her origins, but she doesn't really care. What's important to her is the present.
Personality: Quick-witted and sly, Night Jewel enjoys finding things, acquiring things, and overcoming challenges. She's not afraid of doing things that might get her into trouble - rather, she sees avoiding risks as yet another entertaining challenge. She's also optimistic, and tries to get something good out of every possible situation.
Around other ponies, she's friendly and witty, although she's sometimes suspected of concealing more devious motives beneath this. Given her tendency to get into things she's not supposed to, that is a justified suspicion.
Relationships: Now that she's been in town for a bit, she's made friends with the formerly age-regressed ponies. She's especially fond of Sandy Shore, finding him cute and amusing, and even more so when he gets flustered. She does annoying things around them sometimes, and especially likes to tease Sandy, but is ultimately friendly.