Here you go!
Just a cheap and quick extension to set and unset the cover for KUAL.
As always, look through the shell script files and see what they're actually doing, use at your own risk.
Basically just
copies this image (already in the zip) to /mnt/us/system/thumbnails/ and applies that thumbnail path to ALL of the records (you likely just have 1) that have files ending in .kual, in cc.db.
Reboots after the operation, to refresh the library to get the cover to show.
I'm sure there's a better way to do that that rebooting, so if anyone knows - tell me please!