I recently added an album to my library that had a separate album artwork image for each track embedded in the file. There was an image for the entire album too that I put as the folder.jpg in the album's folder. In the Artwork and Track Details view the artwork for the first song on the album is shown. I think when there are multiple artworks in an album it should show the folder.jpg here instead. Maybe this is already possible or there is a workaround, but I couldn't find one.