[ikiller]

I have had success getting custom screensavers on the Kindle 4 non touch special offers. 4.0 Firmware

Roughly how (using info from this thread as well as others):
1. Plug in kindle, and put an empty file called ENABLE_DIAGS, as well as a folder called screensavers filled with your own screensavers to the root of your kindle user partition. (make sure you aren't hiding file extensions and that the file has no file extension)
2. Reboot kindle and go through debug menu system to start USB networking (see previous posts)
3. Plug the kindle into your computer (I used windows 7) and setup the new network device. Also I found that windows did have the right driver, but I sometimes had to plug it in and unplug it back and forth a couple of times for it to work.
4. ssh into the device with putty, I was using the older firmware so my username was root, pass was mario.
5. delete or rename the .assets folder located in /mnt/us/
6. delete or rename /var/local/adunits directory
7. delete or rename /mnt/base-mmc/amazon/screen_saver/adunits/600x800/banner.gif and screensvr.gif
8. delete or rename /mnt/base-mmc/amazon/screen_saver/600x800
9. create a link from /mnt/base-mmc/amazon/screen_saver/600x800 to your own screensavers (/mnt/us/screensaver):
ln -s /mnt/us/screensaver /mnt/base-mmc/opt/amazon/screen_saver/600x800

I then rebooted and now all of my screensavers from my folder cycle through when put to sleep.