It is an easy thing with iTunes to add what ever album art you like ... copy the cover from Amazon or somewhere and paste it on. I have received a number of files with the WRONG album art on also. If I add on album art with iTunes and put it on LW I do not know if it shows up at the other end. Anyway, as I said I have stopped doing it.
I am going to try and get some album art to show up in LW 4.9.23 ...haven't got round to it yet