If you have photoshop or similar, make yourself a suitable jpeg or gif image about 600x125 pixels in size.
Upload it to a suitable website (eg. photobucket or your own domain site etc etc.)
Add the image link pointer to your signature with "image" and "/image" before & after the url. You need to replace the " by the proper markup brackets
I may help you but you have to swear it will NOT be piccies of the Hoff?
Once you've got piccies online via an online photo album. Photobucket is good.
Go to user options (next to logout)
Click edit personal details/information
Scroll down and there is a box marked signature.
If you're using Photobucket - on the thumbnail page, there are 3 codes for each piccies - URL, IMG & another one. Copy the IMG code and paste into the box