This is a nicely done photo illustration. Having done a multiples manipulation for my digital media class, getting things seamless takes some work. The cast shadows are correct, as are the reflections.
After you mentioned the wall and window, I think I see what you're talking about. Near the corner on the right? Two of my favorite tools in Photoshop for rough edges are the spot healing tool and the clone stamp tool.
The figures are usually the hardest thing to resolve in a photo manipulation because of hair.
Here's a photo illustration I did for my final in Digital Media. Spot heal and clone stamp were my friends here. [link]