This is for the non-touch version of the Kindle 4 only. I was on v4.1 at the time of writing this article. I wrote the article from the perspective of a Mac user. Windows people, sorry.

Access Diagnostics Mode

When the Kindle boots, it looks for a 0-byte file called ENABLE_DIAGS in the root of your Kindle's storage area. If it finds this file it will boot the Kindle into debug mode.

1. Connect your Kindle to your computer via USB
2. Open Terminal and touch /Volumes/Kindle/ENABLE_DIAGS
3. Safely eject the Kindle
4. Restart your Kindle by navigating to [Menu > Settings > Menu > Restart]

Enable USBnet

Now that you've entered diagnostics mode:

1. Navigate to [Misc individual diagnostics > Utilities > Enable USBnet]
2. Connect your Kindle to your computer via USB
3. Open Network Preferences and select "RNDIS/Ethernet Gadget"
4. Configure your IP address manually: 192.168.15.100/255.255.255.0
5. Apply and close Network Settings

Enable Custom Screensavers

Go here to get your root password. You'll need your Kindle's serial number to generate it.

Run the following commands:

You can then disable diagnostics mode and restart your Kindle.

Add Your Screensavers

At this point, when you connect your Kindle to your computer you'll see a new directory called screensavers/. This is the directory that you'll place your screensavers. For them to be recognized the files have a few rules they need to adhere to:

1. Grayscale only
2. 600x800 pixels in dimension
3. PNG format
4. File name must be in the format of "bg_xsmall_ss##.png" where the ## is a number ranging from 00 upwards (01, 02, etc.).

Once you've added your images to the directory, eject your Kindle and restart it.