Well the easiest way is to find a image u like and scale it to 450x140 pixals , then u can just put you name on it
If u would like to do something more complex , I would suggest downloading Gimp 2.0 or a free trial of Photoshop , then adding me on Xfire lol I can teach you a few cool things
If u don't have Xfire , just post any questions here and I wil answer the best I can , online tutorials are very help when u are just starting