Cazzador, there are a TON of tutorials on Deviant Art (
www.deviantart.com). There is also stock art on that website which is free to use in your design (as any copyrighted art or logo is illegal to use without express written consent). Stock art can be anything from photos, fonts, brushes, filters etc.
What you want to do is first create a blank template that is the size you want (and a size allowable by stratics). Save that blank template for later use. What I do from there is fiddle around with a stock image or two, adding effects or color or any number of things. Once you have things looking how you want, you can drop in an image of your paperdoll (if you so choose) and add your "tag". Drop shadows are nice because they add depth and help any text you add stand apart from the background.
If you know anything about photoshop, keep everything within seperate layers because it is easier to go back in and change or adjust things. Once you're finished, you can save two copies of the sig, one as a photoshop file which will retain your layers and things for later tinkering, and one as a jpg. Remember to make the image under 100dpi, as screen resolution is 72dpi.
If you (or anyone) has any questions, I'm more than happy to help out! Just PM me.