The ears should be a little smaller/shorter and the muzzle/head longer and more pointed at the lips, and the hips should be a little longer(and a touch thicker lower down) while the haunch/backward heel should be a bit shorter. You'd also want to make the neck a bit thicker to support the head, and make a larger head, especially around the forehead/jaw though if you want to keep the muzzle small you can just say it's an Arabian to get away with a small muzzle(

). Also the chest a little lower down to at least come close to matching the height that the belly is at where the neck connects to the chest.
If you're going for accuracy and not stylization anyway =3
But the proportions of body length itself are pretty good, like between the shoulders and hips, and you did a really nice job on the shape of the hooves and the hocks(spelling?), I can never seem to get that part right XD And I really love the stylization of the mane and tail
~The Great Me