Magical Realist:
The photo you've linked is poorly digitised. Zooming in even a little shows a heap of jpeg artifacts - so many in fact that I can't tell where this "figure" is that you're telling me I should look at. I can't see anything particularly unusual in the inset photo either. Could you please tell me what this figure you see looks like, where it is in the photo and so on?
According to wikipedia, that plantation is supposed to be one of the "most haunted sites in America" or something. Apparently there have been claims of 10 murders there, but only one is historically documented (not the slave girl you mention, either).
Is this photo really your best evidence for ghosts?
The site has been investigated at least twice, as far as I can tell from a minute or two searching the web.
One of your ghost TV shows - a thing called "Ghost Hunters" (ever seen that one?) - apparently spent a night there. Their infrared cameras saw shapes or images of some kind, although none of the people could see them with their own eyes. The most spooky event reported was when two of the investigators were sitting near a table with a lamp on it, discussing their "research". The lamp slowly was seen in the TV footage to move across the table! Oooh, ghosts ghosts!
The only problem was that the show's own viewers quickly wrote in to express their outrage, because they had noticed that the lamp was being pulled by its own power cord - presumably by one of the makers of the show, off-camera. So much for Ghost Hunters.
The plantation was also investigated by professional paranormal investigator and skeptic Joe Nickell in 2003. A lot of the wikipedia article on the plantation is actually based on his research and the story he wrote back then. He found no evidence at all of any ghosts or paranormal activity there.
The place uses its "ghost house" reputation as a lure for tourists. They even have a web site. They don't want to scare off the tourists, of course, so they make sure to tell you that the ghosts there are harmless to tourists.
There's plenty more information on the place on the web. A lot of it is mindless repeating of information from elsewhere, including all the incorrect stories about the supposed history of the place. But there's some stuff that seems a bit more careful and thoughtful.
Once again, I have to ask you: is this really the most convincing evidence you have for the existence of ghosts? Do you really believe the Myrtle plantation is haunted? By whom? How many ghosts? Why?
Oh, and I should also add that I've found plenty of other "ghost" photos from the plantation house on the web. There is apparently quite a famous mirror that shows ghostly images in some photos. I read that it is cracked and doesn't show the expected reflections from all angles. Looking at some of the photos that purport to show ghosts in a mirror, I notice that some of them merely show direct sunlight shining across one part of the mirror, which looks a bit like a hazy glowing shape if you hold your head the right way and have a good imagination.