I suppose if you wanted to reform your Folder Structure and filenaming conventions you could get Folder.jpg to work by storing stuff in 1 folder per album.
i.e
[Album]\[Disc #] - [Track #] - [Name].ext
There is an expression that looks similar to this but is slightly modified, that you can use to selectively apply the Disc # tag to the file names as well, so it will work for both single(won't insert Disc # field into filename) and multi-disc albums (Will insert the Disc #),or you could just have a Disc 1 for everything, I suppose.. I use a similar expression for sorting my folder structure of my Video library with custom tags.
but I can't remember where I saw it. You could probably find out how to do it by reading through the Expression section of the Wiki
