Click the 'Images' link under the 'Inventory' heading in the Control Panel menu.
If for instance you'd like to delete all images of items sold or deleted over 2 years ago, Select the date you'd like to search before by clicking on 'calendar' icon.
Check all the images you would like to delete from the server & click the 'DELETE CHECKED' button, Or if you'd like to delete all the images within your search criteria, click the 'DELETE ALL...' dropdown menu and select 'Delete all images' option.