For macOS 10.10 and later. This script will look for an image file in the parent folder of each selected track's file--presumably its Album folder in which you have previously placed an image file of some sort--and apply the data from that image file as artwork for the track.
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Append user-entered text to beginning or ending of selected tag of each selected track
downloaded 20m 20s ago
Copy Artist to Album Artist of selected tracks
downloaded 39m 9s ago
Exports and then re-imports selected tracks' artwork
downloaded 39m 21s ago
Gather audio tracks whose files contain no artwork metadata
downloaded 59m 10s ago
Apply selected CD's CD Text to its disc and track tags
downloaded 59m 24s ago
Use tag info from selected track to search Amazon Books for cover art