What about setting the flickr content filter for such images to moderate ? It still allows you to link them, but if someone wants to view them on your flickr photostream then they need a flickr account. It's not that much different than the adult setting of the nexus accounts.
Had this problem too right now and it seem that altough the screen isn't in the imageshare, it will be posted in the forum and it the forum link from my previous screen in the imageshare no points to the new screen.