You still need to work with layers. You basically put some brushes on a background and put a render on it. You should really work with lighting, blur some parts, sharpen others etc..
An example would be this:
I still need to work on that, but I don't have much time right now. Anyway, the thing I want to show you is the fact that the girl is actually popping out. Furthermore, the background has many layers, which is very noticeable. I didn't just put some brushes and a render..