iPod firmware update and graphics hack is possible, and well explained too.
I missed this hack for a while, it's old but it's still hot.
By updating the firmware you can:
1) download all graphics and fonts of your iPod on your PC
2) upload a hacked version ;-)
Be sure to backup all your data before beginning.
The article deals with iPod Photo model, but it's reported to work with iPod mini and 3G iPod too!
Windows users only, this time; you're going to need iPod Wizard, you can get it here.
Remember: updating firmware need cool nerves ... and backup!