If I'm ripping my own CDs - I see what dBpoweramp comes up with. If that isn't up to scratch then I hit Google image search. If I'm still not happy then I fire up the scanner and do it myself. If it's downloaded digital files from Amazon or wherever - I'll check to see if there's embedded artwork in the ID3 tags and extract it with dBpoweramp. Failing that it's off to Google again or the iTunes Artwork Finder site. I tend to find the scanner invaluable for old CD singles and 7 inch vinyl. Half the time the best Google can come up with for these discs is a dodgy looking photo taken from some eBay listing.