It's a nice shot, full of energy but flat as a board. well, perhaps not that flat but it isn't particularly hilly either. Go back and reset your white, black and gray points. I would use the darkest area under the blanket on the rider's right side for my black, the white on one of the cross poles for the while point and probably somewhere around the the area where the rider's right foot is near the top of the stirrup. That alone will do more for this image tahn most anything else you can do. Should just make those colors pop right up, give better separation between the colors and a bit more contrast overall. I'd probably also be inclined to lose more off the right side of the frame.