If you want a picture in your signature all you have to do is find the picture that you want in there, save it to your computer, and then upload it to any image hosting site that you want. (ex: Imageshack)
After you do that just put IMG tags around it and It will show as a picture. Also to make your picture a link all you need to do is add a hyperlink to it. Basically just highlight where you have your link with IMG tags around it, and then hit the "insert link" button on your editing toolbar. After that just add the link that you want and save your signature!
