You can make a JPG, BMP, PNG, GIF, PHP or whatever to display as a picture in your signature by adding IMG tags around the picture link (you need to upload it somewhere, for example
www.imageshack.us or
www.photobucket.com).
I.e. my signature code looks like this:
[img]http://i148.photobucket.com/albums/s25/taderadeva/avatars/sig_drex.png[/img]You can make the pics with your own picture manipulation program (MS Paint, Paint.NET, GIMP, Paint Shop Pro, Adobe Photoshop, etc.), but there are several sites out there to create sigs as well, uh, I see some from
http://ratemyserver.net/ro-character-simulator/index.php or this one is quite popular as well:
http://charsim.rune-nifelheim.com/