OS X 10.8 or 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.
Export artwork of selected tracks to parent or specified folder
Load this script in your Login Items to activate an iTunes playlist at startup
Album-Artist pairs to HTML doc
Continuously update your desktop picture to current track's artwork
Restore each selected track's artwork from an image file stored in its Album folder
Export info to HTML doc