So I copied over my whole site so I can use it as a proper test site with all the add-ons and such installed. Well obviously, that meant deleting all the users and all the threads and post. Just for good measure after deleting everything and everyone, I decided to rebuild all the cache. Good opportunity to empty out the search index and other tables that may still record some old things. Upon telling it to rebuild image thumbnails, which there should be none since I just deleted everything... I see this. Even though there is zero post, there zero threads, and I am now the only user.