Fair enough. There are a lot of nudes in art history though (and depictions of Jesus), especially among public domain works. To be comprehensive, I'd have to go through and manually tag as nude/non-nude, which I have not yet done. Something for the future, perhaps when collaborative filtering gets rolled in. For now, you can try selecting everything but "nude painting" from the Genres list. That may help. Alternatively, maybe select an artist known to be "safer".
This might be a good use of Amazon Mechanical Turk. It will need to be manually done by humans but you can do it at a very cheap rate by crowd sourcing it.
I know it's art but everyone else just sees nudity.