I wrote a VERY simple screensaver hack. Like the usbnetwork one, it's very minimal and only does what it says (no advanced features).
It's not for and doesn't work on special offer kindles, so don't even ask.
Now it's important to follow the naming rules or the screensaver won't show up or worse, the screensaver module will crash and you need to restart the kindle after you fix it.
1) Each image MUST be a grayscale PNG that is 600 × 800
2) Each image MUST be named bg_xsmall_ss##.png, where ## is a two digit number from 00 to 99
3) You MUST have an image named bg_xsmall_ss00.png and you CANNOT skip a number (ex: bg_xsmall_ss00.png, bg_xsmall_ss02.png but no bg_xsmall_ss01.png)
The image displayed is in the order of the number
(You CAN delete, replace, and rename images already in the folder. They are just copies.)