After a bit of digging on my own I found this…
The iTunes folder art files are stored in your iTunes directory under
iTunesAlbum ArtDownload then some weird mumbo-jumbo-y numeric names which probably are listed in the iTunes playlist or other type file as to which song files they belong to. In general there’s one subfolder under ‘Album Art’ then a three-deep heirarchy of folders with names all ranging from 00 to 15. Much like how the iPod stores it’s music on its internal hard drive. But to get to the point, under the 3rd deep folder (i.e. iTunesAlbum ArtDownloadCDO12343 02334) there are *.itc files. These are basically JPEGs with about 500 bytes of a weird header. If this header is removed you are left with *.jpgs, but I guess you wouldn’t know which ones unless you looked at the iTunes playlist file or something.
In order to get *.jpg files out of the iTunes library you need to remove the first so many bits of data from the *.itc files. In Windows I found that you must remove the first exactly 500, but I believe that for folder art created by Macs it is 493. I do this in Windows using a hex editor (XVI32). But here’s a link to how to do this on a per-file basis using the Unix or Linux tail command http://marv.kordix.com/archives/000917.html.
Sorry if that was a bit confusing…