PSP-Hacks.com

Description:
Slasher's homebrew app to easily flash modified XMB waves (system_plugin_bg.rco files) to your PSP.

This is for just about any custom firmware version, including 3.03 OE-C, AND 3.10 OE-A. I've heard reports of this bricking 1.5's, so I wouldn't risk it if I were you.

See readme.txt for instructions on usage.