ok. I will give a critique.
I don't do computer art, so I can't crit there. But, the very first thing that stands out is that the horse's skull is not "true". I mean, its' eye are not in the correct alignment to match that of the nostrils.
When the head is turned at an angle, like that portrait, it's very important that the angle of the nostrils (If you drew a line from the center of one to the center of the other) be parallel to that of the eyes. Yours has the horse's right eye a bit too low in it's skull. The resulting effect is that the skull is too "plastic", kind of warped .
I also think the jaw of the horse is a bit too small.
The modeling of the light/shadow is good and the overall composition is good.