This my biggest reason to hesitate recommending nostr. This shouldn't be something people stumble upon. Block/report the user, report to the image provider, remove the relay. Nostr itself doesn't hold the images, just holds the text links. Some services like nostr.build and likely other relays will pre scan and also file reports.
Discussion
Dumb but honest question: when you report a user, who exactly are you reporting to since there is no centralized hub/server ?
You're reporting to relay operators, signaling to other users.
https://github.com/nostr-protocol/nips/blob/master/56.md
Nostr has no centralized authority, meaning the power and change comes from its users. We have more responsibilities as users and developers to keep this out of other's periphery.
The problem lies when images are hosted externally. We can't do much about that besides reporting the user. If you're feeling ambitious you could contact the place that the image is being hosted, but this also requires a lot of work for the use to do. It sucks.
I think we need to make NIP-56 more robust ASAP. Users shouldn't have to investigate wherever it came from, it's traumatizing.
More clients could look into implementing some sort of support or reports, similar to what Amethyst does, IMO. This includes giving users the option of disabling the feature. This puts the community in charge of moderation and in charge of their WoT.
And that is going to go perfectly well and won’t cause a problem when anyone asks people to mass report what they don’t like
Primal does no media moderation this has been an open secret for a while
Somehow nostr:npub137c5pd8gmhhe0njtsgwjgunc5xjr2vmzvglkgqs5sjeh972gqqxqjak37w and nostr:npub13ch6rllnruy5z2qm57836yw5zx4ytju4jl569jys6jhtp9furupsccdsaw have managed to do way better than them with none of the funding
This only works for nostr-related hosted media though. It's a band-aid fix at best as it excludes 99.99% of the Internet.
Recommending Nostr is like recommending the internet.
Recommend communities (relays) instead.