I just found out today that firmware has hidden support for a random screensaver image. If you add a directory called "screensaver" inside the ".kobo" directory, images in it will be selected randomly to be used as the screensaver.
The steps needed to use a random image for the screensaver are:
- In the ".kobo" directory, create a directory called "screensaver".
- Put the images you want to see as screensavers in the new directory.
- Disconnect the device.
- In the settings, on the "Energy saving and privacy" screen, turn on "Show current read" and "Show book covers full screen".
- Put the device to sleep and see one of the images. If there is only one image, it will always be used.
This came up in a discussion elsewhere that was sort of triggered by the current miniclock discussion. It has been in the firmware since 4.13.x without anyone noticing.