TuneUp uses the application programming interface (API) published by Apple and Microsoft to add metadata and cover art to iTunes and Windows Media Player. This API unfortunately doesn't allow 3rd party applications like TuneUp to remove cover art from music stored within your iTunes/Windows Media Player library.
To delete Cover Art manually:
1.) Highlight all the songs for which you want to delete cover art in iTunes
2.) Right click on these songs, and select "Clear Downloaded Artwork" from the drop down menu that appears
Windows Media Player:
While Windows Media Player does not have a built in Cover Art removal feature, many of our users have success removing Cover Art with the following plug-in: