I restored my banshee db as per this question. My music and listening history shows up as expected, but the cover art is missing, and Banshee won't scan for it. "Rescan music library" doesn't check for cover art. Neither does disabling/re-enabling the cover art plugin. I can't find an option to do this--is it possible?
The covers are stored in ~/.cache/media-art/ You might try renaming the folder to force Banshee downloading the covers again. I haven't tested the solution, so don't delete the folder alltogether.
Try typing in a terminal:
This will make banshee download missing covers.
Banshee stores album covers in
~/.cache/media-art. If you copy that folder along with the others, the covers should all be waiting for you when you open up Banshee.