I think you have made the horse better looking than it is in reality. The neck on yours differs from the photo, but perhaps you did this on purpose. And I like the way you adjusted the front legs to make the horse more engaged and balanced.
Not really much to suggest because it is not finished. I guess just to say, don't overwork it because your style has a certain freshness to it that is easily ruined if you worry about making every line clean and perfect. I know, it's the artist's perennial dilemna; when is it finished? When to quit.
This is a very nice piece. The owner will be thrilled
I originally drew the pose off a blend of her reference pictures and I'm using a different one for the shading, so that's probably why the neck looks off. I wish I had just stuck to one picture though, it would have saved a lot of brain damage!