If my account is set to “not at first”, other users should not be able to send pictures unsolicited. I can’t stand being continually harassed with unwanted images because respecting my choices is optional for the sender.
Obviously we can’t monitor the image content constantly, but perhaps a prompt on sender end to inform them of my account setting such as;
“This user has stated they do not accept NSFW pictures at first, send anyway?” Since most don’t even read accounts before sending, as a deterrent. Maybe paired with the ability on receiver end to hide thumbnails of images sent anyway, and decide to open them or not?