It seems Sony is taking a lesson from the homebrew scene. The latest revision of the PSP firmware (3.71) included the feature of custom XMB themes. To help make customization easier Sony released a tool which allows you to create your own custom theme. The theme will work on the both the official firmware and M33's custom firmware. Simply place the .ptf file into ms0:/PSP/THEME and select it from the theme settings menu. A manual is included for those with little to no experience making themes. Credit goes to zmcnulty for translating the manual into English.