I'm almost certain the background is just bad photoshop work. Swapping the heads which are far different in proportion left a bunch of blank space needing to be filled in.

But that's just a hunch.

Edit: the more I look at it, the heads don't even seem to be from the same photo, possibly. The skin / hair tones seem off. And I'm not as convinced weird background patching needed to occur. What a strange picture.