Need help quickly placing a banner at the top of my theme!

I’d like to make a banner fit at the top of my page similar to this site http://jaywaninc.com

My website I’m currently working on is http://bigboyzmusic.com

I pretty much want to create a gfx design and size it to match the body of my posts and navi bar…

A little assistance would be greatly appreciated I tried some kind of hack code but it didn’t work and so far the plug-ins for banners suck unfortunately 😉