If you haven't heard of them already, they're so good.
http://www.getpersonas.com

so easy to make, and so easy to preview.. once you've download the add on for it (200KB) you just select any persona that you like and hover over it. You've instantly got a new skin for firefox
That's one good reason why i'm using firefox

Have a look at the one i made:
http://bit.ly/BTund

There are so many to choose from, and your bound to find one that you'll like