Here’s a TIP on How to Fix Missing iTunes Album Art:
Sometimes iTunes “Get Artwork” function does not get the right album cover artwork, or even worse, sometimes it doesn’t get any. One can fix this pretty easily via this nifty (free!) Dashboard Widget:

“Amazon Album Art widget makes filling in the gaps in your iTunes album art collection a breeze. Search for album art from Amazon’s comprehensive catalogue, then import it into iTunes with the click of a button.”
Whenever iTunes doesn’t get the right album artwork, I just select the song and open this widget in DASHBOARD. It checks Amazon for images and you just choose the Album Artwork you want and “Set as Album Art in iTunes”. Easy. And Brilliant.

This is definitely one of the most useful Dashboard Widgets I use. Try it whenever you find just black in iTunes where your nice album cover should be.

