Well, to be honest I don't like it. The render is blurred and the bg is sharp which draws your eyes to the bg instead of the render. Also, the bg is too messy. I would suggest checking out some tuts here. They help a lot.
what he said, also when i look at it, nothing has been done but a render placed over a terrible background.
You need to find a balance between blending/matching your render to the background and contrasting/making it stand out. Just keep practicing and you'll get better.
