I don't know much about making tags and stuff, but to tell the truth.... ..It looks a little plain....
Okay, let´s see... Well, the sig looks like the render is sorrounded by clouds, it needs more colors, maybe a CD4, oh yeah, and the text looks almost invicible.
The background is really, really, really repetitive, aside from from the C4D. The part right over his right shoulder looks good, though. xD The light source shouldn't be as far to the right as it should be. You should have moved the text to match the flow of the rest of sig. If you want to keep the whole B&W thing you should make the red in the C4D a little more dull.