If you konw how to make sigs, here are some some renders by Planet Renders.. It is the most, and best in my opinion site.
You use Renders to make sigs. like my current sig, I got the CoD 4 player from that site.You just have to make a background or find a background like i do.
If you want to learn how to make sigs, try youtube'ing "GIMP SIG TUTORIALS". That's how I learned how to make.
-Note-, this site is copyright free, so you can take any image.