[pkscout]

I gave your latest version a try - script.artistslideshow-2.1.0.alpha5-installer.zip
 

If you still have the debug log for that upgrade attempt, I'll take a look at it.  Here's the process used to do the upgrade:

1. AS gets a list of all the folders in the ArtistInformation directory.
   
2. For each folder, AS tries to parse the fanarttv file for the artist name.  If that doesn't work it tries theaudiodb file and then the last.fm file.
   
3. If there's an artist, AS renames the ArtistInformation file and the corresponding ArtistSlideshow folder.
   
4. If there is no artist, AS moves the two folders (and their contents) to an archive directory.
   
5. AS then gets a list of all the new ArtistInformation folders.
   
6. For each folder, AS grabs the image URLs for each service and hashes the URL.
   
7. If there is a matching image with the hashed name in either the ArtistSlideshow folder or the local storage folder, it renames it to the original name the service uses and puts it into the _imgdb.nfo file (that tracks what has been downloaded).
   

AS does some other work if you select to only use local storage for images, but that's the gist.  If you have image folders that didn't have a corresponding ArtistInformation folder, they are never touched.  They'll never get used again, so you can delete them or manually rename them if you know the name of the artist based on the picture.  I've also found that some of the old ArtistInformation folders are not archived, but there isn't a pattern.  Again, you can jut manually delete or rename those if you want.  The process isn't perfect, so I'm not surprised there are some left over directories.