I did. Just playing around with it...
Alright, this is what you do.. First, save the picture to your computer... Go to your profile, and find Upload signature image under your signature space... Browse your computer, select the picture and upload. You'll receive a tag complete with IMG brackets. Copy that and return to your profile. Paste it in your signature bar. Remember, you have only nine lines for space in the signature, so you may have to minmize your text to one line