I like that horse a lot! And congratulations for a nice inspirational reference
Here are a few suggestions to make it more horse-ly:
Check the proportions: body to leg height, hoof placement, angles on the leg parts.
Add more contrast between colors/Remove unnecessary colors.
Remove interior contour lines (as in, everything that's not separating the inside from the outside).
Use a defined lightsource.
Added more leg height, changed the anatomy (angles, distance between legs/hooves), tweaked the colors and added a lightsource (not too happy with that last one though. I'm kinda rusty).
Good luck with the game! Looks like you're quite energized about it, hope you learn a lot and make it happen!