i think you are starting to get there with merging renders with real life backrounds. What I think you need to work on is getting the lightings to match up. The best way to do that is find a good picture with a lot of lighting that you can tone down if you have to and just mess around with it in photoshop. Still I think you are getting the hang of it.
It's quite nice, but I'd make the render cast more of a shadow on the surroundings. Really interesting style you're developing here with your 3D work.
Hm, interstin...not so sure about the bg but the renders pretty good man