Amazing job modelling. If I'd have to point something, as constructive criticism, just bothers me a bit his upper left leg. I know the anatomy is not exactly accurate to a real horse, because it's not a real horse, but legs on horses, zebras, donkeys and those animals doesn't bend their knees backwards. You didn't bend it so much, but looks almost as if it was going to break. Maybe that was the impression you wanted to give, but I've been riding horses for almost 18 years and for me is a bit awkward , specially when you see the other kness bending in the right way (thinking that he could bend his knees on both ways makes it weird to imagine walking).
I know if I made sense with this, english is not my mother tongue ...
Other than that, I assure you the figure is really good. Specially the way you did the face and teeth!
I remember this Discworld novel where these dragon riders dismounted their dragons up on the ceiling of a cavern and then "walked" on the ceiling by using boots with hooks on them to grab rings on the ceiling. When I saw this horse I thought, "Now, they could just mount this horse to get to and from their dragons." This would make a fun mount for a subterranean species/culture looking to make the most of their space by mounting rings in the "roads" above as this animal could go on both top and bottom.