Okay first things first this is a reall wonderful picture made by a really wonderful gal!
It has shading lighting and perspective.
But there are some things that i must point out the ear on the right (from our perspective) seems to be farther down on the skull than the aer on the left, I'd suggest leaning it in farther towrds the crown.
Secondly, I know this is a tiny flaw and actually gives this picture character, the jittery-ish lines on the leg,the just seem sort of off in a way.
And last,this si just something that bothers me but isn't really a flaw,the neck is shrt to non-existant!
Horse and pony necks are long and majestic.
But overall this is a terrific piece that I will come back to and stare at for inspiration!