[SparrowHawk]

It's not just about the renders. Well, sort of it is. You need to make the render blend in with the background, support it. Get some C4D renders to spice it up.

Look at some sigs here Showcases They may be mostly photoshop but I believe Gimp can do the same thing. See what they look like, go into random showcases and look.

Don't take any and claim them as your work though :/ Most disgraceful thing an artist can do. Be not a fool.