He looks thoroughbred, except for his head. The roman nose makes me think he may have draft breed in him. Hoepfully someone else can offer better help than me, though. Good luck on your analysis. I can't wait for my semester to end here.
He doesn't look at all like a Quarter Horse!
I think he's a French Trotter (I don't know how to say it in english in french it's Trotteur Franšais ) He looks like one anyway (the head, and the fact that it's a racehorse...)