itunes artwork issue

Most odd then. You can try holding down ctrl+shift as you launch iTunes which can sometimes fix up odd indexing issues. To reset the artwork cache delete the Album Artwork folder inside your iTunes folder then launch iTunes and slowly scroll through the whole library in a view that shows artwork.

tt2

As noted earlier while you may add images to individual songs, if two or more songs are considered to be from the same album (same album title and artist or album artist) then iTunes will use the image from the first track that has artwork everywhere for that album.

tt2

I'm not entirely certain that I've understood your issue, but iTunes typically associates only one image with an album, even when different songs from that album have different images associated with them. If you want to rebuild the iTunes artwork cache delete the folder Album Artwork from inside the iTunes library folder, then scroll through your library in say the albums view to prompt a rebuild.

tt2