You can make one from Paint if you really wanted to, its what Baked does.
Best starter 'free' program that I used was "GIMP" type that in Google along with how to make a Sig, and you should have all you need to start.
When finished, you just upload it on to a site like PhotoBucket/ImageShack etc, and use the code created.
Unless you want one made for you, got to this thread; viewtopic.php?f=6&t=436
and someone will create you one, just leave a few details on what you want added