OS X 10.8 and later. This script will export then re-import the artwork data of the selected tracks obliging iTunes to embed the artwork in the track's file's meta-data.
Note: this app does not affect how the Finder may or may not display a file's icon image.
Also see Tracks Without Embedded Artwork.
Search allmusic website (AMG) with data from selected or playing track
Move selected playlists to a new or existing folder
Search YouTube using tag info from selected or playing track
Gather audio tracks whose files contain no artwork meta-data
Export album artwork as folder.jpg to Album folder
Applet assists with swapping, copying, appending data between track tags