click this:
http://www.importatlanta.com/forums/...=editsignature

then go to tinypic.com and upload your picture, make sure you copy the stuff in the "Direct Link for Layouts", then paste it in the box for your sig . for example if i wanted this badass image of popobawa in my sig, i'd do:
[img*]http://i31.tinypic.com/5017qw.jpg[*/img] except, take out the * and you end up with