A couple of composites...

Never tried doing composites before but I decided to give it a try. Here is the original photo...

I'd say the main thing you should work on is edges. I'd say smooth out some of the white pixels that make your original photo very jagged along the left side. Also, color the white highlights on the left edge to cool them down a bit. They make it very noticeable that the image has been altered, as there is no light strong enough to produce the harsh shadows that the person has.

Also, for the composition of the images, I honestly think that sizing down the person would help quite a bit. It looks like you don't have a lot of room for that, but even a little bit would help.