iSwitcher lets you change out iPhone themes and make your own. I think they have it rigged up to make a theme on your phone as well. Just google it, read the threads on here and ModMyiPhone.com. I use Pixadex to keep track of all my icons, like iPhoto for icons, and the just export 60x60 PNGs from Pixadex. There are plenty of icon sites so you can just mix and match them if you like.