With MW1.35, We can deploy https://www.mediawiki.org/wiki/Extension:MediaModeration. This works with an API to scan uploaded images to detect and warn about issues with Child Pornorgaphy, Terrorist Content and other potentially illegal images.
It is security approved as WMF deployed and @Owen has confirmed that from a legal stance it's fine and emails can be sent to him.
We need a key for the API before doing this so tagging #sre to add it to PS.php
Please stall when they key is added.