I have read a number of posts here about the inability of iTunes to display album art for anything but music purchased thru iTunes. I have come up with a solution for Windows users: I imported a few of my CDs and then went to the All Music Guide website (allmusic.com). I then looked up the CDs I had just imported and then right clicked on the image of the CD cover and selected 'copy'. I then opened iTunes selected all the tracks in that particular CD and right-clicked again on 'Get Info'. I then right-clicked on the 'Artwork' square and pasted.
I hope this works for some of you. Actually, I just hope it makes sense to some of you. I did notice that the image is not quite as clear as the iTunes artwork, but it looks good enough for me. I also first tried Amazon.com but they sometimes put little "such and such % off" stickers over the album art. Allmusic.com is the best I have found so far.