This painting has a beautiful, almost eerie quality to it with the soft lighting. I love that the background is soft and, as you put it, unfinished. I think it gives more importance to the horse and cattle.
It appears the horse is back lit which is very dramatic. That said it would be interesting to see what would happen if there was more contrast around the face and mane just to give it a little more "pop". A soft pop but enough to really draw some attention to that well painted, beautifully dappled horse.
Any detail in the foreground should be limited to just around the horses front legs with only a smidgen of saturated color - again- just to pop that focal area.
Anyway, that's my 2 cents.
Love what you did and I see it was over a year ago. I wonder if you ever did make any changes or left it as is? :)