Retrieve Album Art?

If you go to the menu bar > retrieve album artwork and it can't find any artwork for your album/ track then the simplest and easiest thing to do is to find it on google images then copy and paste it into the album info section by right clicking on the track > get info > artwork and paste into the big white box. Then just click next to go to the next track and then paste again. The shortcut for past is ctrl + V (PC) or cmd + V(Mac) if you want to speed up the process.

Hope that helps