Since ARRM 2.0.3.0 Beta 1, it is possible to delete all or part of the MEDIA.
Select the desired system and click on the 'Show' button
The gamelist is displayed
Select all or part of the Roms to process
Click on the 'Remove Artworks' button in the 'Possible actions on selected Roms' panel. The data deletion will be done on the checked Media and the selected Roms.
A popup will ask you to choose the MEDIA to delete
Click OK to start processing or Cancel to quit
Wait for the processing to end.
Save your gamelist by clicking on the 'Create gamelist.xml' button in the 'Gamelist' panel