We love mods, and this one is on our short list. iGameboy is a theme mod for jailbroken iPhones. There's both a button and a full-screen version (I'm partial to the button theme myself). As of this writing, the author, Rob Sheridan, has produced 45 icons to accompany the theme, so chances are your apps are included.
The full download even includes instructions and basic files for making your own icons. Nice work, Rob! We love it.
While we're on the topic, here are some other iPhone mods we liked.