I've tried this and it does work. I put a Super Mario theme on my iPod!! w00t w00t!!
Tut by Lethal_B.
THINGS YOU WILL NEED
<1> A Colour iPod (iPod Nano, iPod 4th generation
Photo, or
iPod Video)
<2> iPodWizard. The latest version is v1.2, and the
download can be found through this link -
http://sourceforge.net/project/showfiles.php?group_id=153441
<3> iPod Firmware/Updater. I recommend you guys use version 1.0, as it is the most stable. The download of iPod Updater 2005-11-17 v1.0 can be found here -
http://www.megaupload.com/?d=Y44N4BER
<4> iHack -
http://www.ipodwizard.net/attachment.php?attachmentid=3392&d=1127... NOW TO BEGIN..
<1> Extract and load your iPodWizard Software.
<2> Click
"Open Updater" 
<3> Load the iPod Updater that your just downloaded. I recommend v1.0 (2005-11-17), but it should work with any other Updater.
<4> Under the "Firmware" menu, select your model of iPod.
Once you have done that, click "Load".
<5>
(i) Click on the "Firmware Editor" tab, followed by the "Pictures" (ii) tab. You will now have an 'index' (iii) with a dropdown menu showing you each and every
graphic that is written onto your iPod's firmware.
We can modify these graphics and write them to the Updater, and once we synchronize our iPod using the Updater, the modifications will appear on the iPod aswell.
CHANGING THE GRAPHICS
There are a couple of methods you can use to modify the graphics.
You can
manually edit the bitmap images..
Select an image you would like to modify/replace from the drop-down menu, and click "Save Image" (Located to the right of the interface).
This will save a copy of the image in .bmp (bitmap) format to your HDD. Open the image with an image editing program such as
Photoshop, Macromedia Fireworks, or even just the basic
MS Paint -- and edit the image to whatever you wish.
Remember though,
Don't change the image’s dimensions!. Once you have finished, save the modified file and use the iPodWizard "Load Image" function to replace the existing photo in the firmware image. Repeat this process with each graphic you wish to change.
Alternatively, you can load a whole group of bitmap images that have been prepared as a 'Theme'.
To get hold of themes for your particular iPod, the best source to look are the
iPodWizard Themes forums -
http://www.ipodwizard.net/forumdisplay.php?f=17
Once you have downloaded a 'theme' (which will consist of a .zip/.rar file filled with bitmap images), then extract them into an empty folder. (Please be sure that the themes you download are created for your firmware version, as the order & number of graphics varies with each update).
Then, click on the "Load All" function in iPW, and load the folder in which you extracted the 'theme'.
WRITING YOUR THEME TO YOUR FIRMWARE
Once you have finished tweaking with your bitmap images, you are almost finished. Click "Write" which is located at the very top in the center.
Once the confirmation that the changes you implemented were sucessfully written onto the updater, You can exit iPodWizard.
TRANSFERRING TO IPOD
All you have left to do, is simply connect your iPod to your PC and use the "Restore" feature on the Updater to rewrite the firmware with the modified version.
However, if you don’t want to "Restore" your iPod (Which deletes all content), You will have to patch the Updater with
iHack
iHack will set the iPod’s firmware version a small amount below its current level before you run the iPod Software Updater, re-enabling the "Update" button. Open iHack (you will find it at C:/Program Files/iHack/ by default), and click the "Patch..." button while your iPod is connected to your PC and the
disk mode feature is enabled. Select your iPod’s drive letter, and iHack will do the rest. Now click the "Update" button, and you will have successfully changed the graphics on your iPod.
Changing theme of your iPod
