The highpoints are definetly the side lighting coming in and the long shadows. While I like the pose of the head here and the lighting of the main, the rear end is a low point for me. The exposure is good, looks like you were trying to preserve the highlights here. That's good, just not enough highlights in the photo, most of the exposure is in the basement. A little contrast/brightness would help. However, I think the main thing here is the position of the horse, just a slight turn so it embraces the light a bit more and you would have had something magical. As is just an average rating from me. A terrific idea! Hope that helps.