Here's my current best, I'm using it now:
![Image](http://oolite.ryanhoots.com/tmkksig.png)
The image is of my customized ship in a space game I play.
Signatures are 100x400 pixels, hosted probably on Picasa, if you have a server you can host it. All I need to know is text (if you want any), background color, theme/design, and maybe a base image if you want one.
One signature image is $5.