I always try to incorporate a very high contrast. Which is blatently apparent in my own signature. Another really nice thing is to have some perspective, so it gives your signature more eye grabbing features. A lot of the time, i try to avoid grey, unless that's the specific genre of the graphic. The signature that you have now is filled in pretty nicely, however the new red one that you made, feels kind of empty to me; as though you might be able to put somthing more within it. I'm going to upload all of the signature graphics to a page so you can see some examples. I'll post the link here when I get it uploaded.