Banned for quoting me in your sig(im really just posting cause this is getting dangerously close to 100 pages, and i want to be the one to get it there) Edit: damn!
http://forum.tip.it/viewtopic.php?p=3071374#3071374 Try this, if you dont like it theres other tutorials like it here and all over the great and vast internet.
When you make pencil sigs try to use the drawings as you would use renders, like these iv made: Try putting an acual background on it, and a border, and get rid of that other part of drawing in the corner:P