I'm no artist, but in the spirit of the thread here's my 2 cents: the snout is too narrow for a male pony, the eyes need to be a bit larger. The left hind leg looks like it's behind the belly because of how the lines intersect. All in all a solid first day. I wouldn't start adding detail yet, it distracts from learning to draw the general shape consistently pony-like.
My own (not yet submitted) submissions to the ATG:
I tried to be inspired by the structure of real horse armor. I still have trouble drawing... anything, really. Inked with a marker, Photoshopped for color and better contrast.
This was fun, if too time-consuming. I have this habit of aiming too high. I shouldn't be trying to draw crossovers yet, I still have trouble with eyes and poses... Pencil sketch > phone camera > Paint Tool Sai linework layer > another layer for colors.