The story so far. Music album art has been a nightmare on Symbian since day one. CoverUp appeared in 2010 to solve the problem by raiding Amazon's pages for matching bitmaps that could then be poked into Music player's library. It worked well, but the developer (Sebastian Brannstrom) wanted to do more, so he rewrote it in QML, in order to better share code with the version on the N9. Alas, the scale of CoverUp didn't work well in QML and was very restricted ('memory error', etc), so Sebastian went back to his 'old' Qt code, fixed a few things and - we now have CoverUp back in the Nokia Store - hooray!
If you haven't got CoverUp installed already then just buy/install it as normal from the Store and you're good to go - it should find most of your missing album covers in a minute or so.
However, if, like me, you had the new (problematic) version 3.0 installed then you've got to be a bit more careful:
Veryify that you can see CoverUp back in the Store again - you're looking for v2.3.0.
Ignore it for now. Long press on the CoverUp icon on the main Symbian app menu and choose 'Delete'.
You'd think that v3.0 was gone, but not so. Knowledge of it is still cached in the Nokia Store client, it seems - installing the reinstated v2.3 now will actually install v3.0 again - go figure. It happened to me. Instead, power the phone right down (forcing the Nokia Store to quit and all temporary files to get zapped).
Now go into the Store and install CoverUp. The correct version will come down and install.
Run the app and start to fill in your music collection album art.
Left, version 3 in place and - problematic, at least with my music collection (about 100 album's worth loaded onto microSD). Right, deleting this version.
At this point, I had to power down the phone to flush Nokia Store's temporary files. I then restarted and went into the Store again and downloaded v2.3.0 for real. After installation, right, it shows you your albums and the extent of your 'missing' album art.
After 'Finding missing covers', most now have artwork, and nicely done too.
Pressing 'back' or using the appropriate menu option then 'Stores' the new covers in the Symbian Music library, where (right) they can be seen immediately by Music player.
Sebastian is promising a full write-up of the whole saga on a blog soon - we'll add a link here when that appears.