The black background equine portrait to me is an absolute classic. I LOVE them to the point that I want them on canvas wall mounts for all of my clients. If and when done correctly these photos are stunning and highlight the neck and subtle coloring of the horse. They can be done just the horse, you and your horse, dog and other pets, and to highlight the barn itself. It's mostly done in camera and then touching up in the editing phase.
Most of my clients have no idea how hard they are to edit though. The general outline is there in the shot and needs to be enhanced. But it requires several hours of careful touch ups within the editing and a really gentle hand to make sure a line isn't crooked, that you don't lose the black details on the horse, that the eyes capture light, and that there isn't any big distraction in the shadows.
Within the photography community there is a lot of controversy about these black backgrounds. Some people love them and some people feel they are over done and too much post editing is done to them. It's definitely a personal preference per photographer - so if you like them make sure your photographer is comfortable shooting and editing them and enjoys doing them!
What do you think of black background portraits? Is it something you would hang on your wall? Contact me if you have more questions!