Display which images and documents are being used in campaigns

I could delete sooo many images from the library, if I knew WHICH version of a photo was actually used in an email. Every time I edit a photo a new image is added to the photo library and I don't have time to delete older versions at the time I am writing emails because I am pressed for time, but I would love to go back and delete images that never appeared in an email. A feature such as some kind of highlight of images actually inserted in a newsletter would help REMOVE sooo much memory being taken up by unused images - that should be a HUGE bonus for you if everyone could do some housekeeping in their images.