Now for something a bit geekier

I managed to get a theme I've had my eye on for a couple of days and with a quick Google search, also managed to find out how to install it.

I like it and it was easier than I thought to install. Remember to backup any files you're about to replace.

/!\Warning!/!\ Although a fairly easy task, there is still half a chance of bricking the PSP. This 'guide' is for M33 3.51 Custom Firmware themes ONLY, do not attempt to install any other themes or icons that haven't been flashed for M33 3.51.

{Edit} My PSP is a standard install that hasn't been updated to M33-7, so I can't tell you if it works on the latest update or not.

1. Connect the PSP to your computer with the USB lead, hold down the Right trigger and turn on the PSP to go into Recovery Mode.
   
2. Go to Advanced -> Toggle USB (flash0) and the box should pop up.
   
3. Once in the directory, open the vsh\resource folder and copy the .rco files and .bmp image of the theme over.
   
4. Go back to the root dir and go into the font folder, copy over the pgf file.

That's it, exit from Recovery Mode, go into system settings to change the theme and away you go. Remember that you'll be overwriting some files, so if you want to replace them at a later date, keep them backed up somewhere safe.