Although there is an option to delete messages and images sent in the private messaging system on the site, I often find that they take FOREVER to eventually appear as blank with the word 'Deleted' in them. I've actually asked people hours after sending images in the past and deleting them if they can still see them and they say they can. This should be instant and for both parties. Sometimes you send something you may not wish to stay there on the chat forever...on view for the other person to see. It should be instant for peace of mind if nothing else.