Depends on song file, but AFAIK, I had thought many album art is imbedded within the song file's id3 tag (mp3 tag). I am aware it is separate for some song files.

However, I have noticed iTunes uses an album art cache which I have no idea what it is for. The files within have an extension of .itc so I guess if your album art has a similar extension you could add that extension to your Word filter within LW. Not sure if that would help though.