Now, I couldn't actually believe at first I could critique on a picture. Then I realized it wasn't one! XD First of all, my apologizes, I am the worst at critiquing, in my opinion, so feel free to rate this unfair! (:

Anyway.....
I love this piece! ♥ The colors are all well suited for the horse, and are merged it nice, and the shading is great! (:
I've only got two things -
Firstly, that mane looks a *tad* short. Maybe a bit longer, not too much, should do the trick!
Secondly, the scars on the front are well done, but I think the white is a bit to light/harsh. Maybe soften the color up a bit or make it a pale grey.

Other than that terrible advice, I think this is amazing. I wouldn't even dream of drawing this, let alone painting it digitally. XD
Remember: I think this critique is terrible, so feel free to make this unfair! (: XD

~ WA