The actual C4D work is done quite well, the shading and lighting works well. As for the image as a whole, this is where the downfall is. The first thing i noticed was the render is not horizontally straight (slight rotation would fix). Next is the overlays, they seem unneeded in this image as a nebula stock overlayed on grey gives no illusion. As for external lighting, this image seems to lack any form of light source. I would scrap the nebula overlay and try to go in a different direction.And always remember to stick with one theme.