UPDATED: Restore Artwork from Album Folder v4.3
For macOS 10.15 and later only. 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.
Also see Save Album Art to Album Folder and Save Album Art as folder.jpg which assist with exporting album artwork as image files.
Latest version:
- Additional accommodations for macOS 11 Big Sur
More information for Restore Artwork from Album Folder v4.3 and download link is here.