Nice reflections but one major problem... You put the background in in photoshop didn't you? Unless you need it to be anything other than a simple gradient, Use C4D for the background. Alpha works... But its not perfect. The edges between opaque and transparent aren't as smooth, if you did the background right in C4D. And photoshop's gradient tool isn't very good for some reason. As you can see the polygons created in the background. Finally, with the background gradient, you should have started with a darker gray, and went to black.
Heres a similar work I just made a few minutes ago. [link]