go down to the "my signature" box, and then start throwing in HTML.
If you want a pic, you use image tabs in html like this:
the "src" is short for source, the URL of the pic.
you can get jiggy wid it and resize the image using other quantifiers within the tag, like width and height
You cen get even more jiggy wid it by making the pic a link, so when you click on the picture, it will take you to a website. The tag for this is the "a" tag. The quantifier within this tag is the href, which is short for hypertext reference:
And if that isn't jiggy enough, you can even control where all the pics go by using tables and stuff, but it's hard to fit all that in because they only let you have 255 characters in your signature box.