I don't think a bot could get this kind of vandalism. Using a page
blanking bot could be nice but most work has to be done by humans.
I am happy to notice when I am patrolling new edits I get a often a edit
conflict with somebody else that is also reverting the vandalism. But I am
afraid not everything can be found while paroling.
Does Flagged Revisions also works on images?
Best regards,
Huib