A little too overexposed. The contrast is just too much because of it. I like the concept, as I was going to do something like this as well!! But I didn't
first, I like the simple framing of this horse. Three things I object to are---I don't like the rope dangeling from the bit---the post behind the front legs---and the green and brown whatsit behind the head..........
Find a way to point your camera that makes us see the horse as more than just a horse - what is it you want to say about the horse in general or this horse inspecific? Strong? Big? get down below the horseand point the camera up to it. Tired, Hot? Put that sleepy eye at a central part of the composition. A great way to explore senic trails? Put that horse in a spot with a senic background. Fun to ride? Put a happy, energetic rider on him.