I played around with the idea, but ultimately came to the same conclusion as fire.
Moderation also becomes a whole different ballgame when people are presented with full-sized images without prompts.
When a mod reposted my submission while I was sleeping, when I woke up some people had spammed bestiality. If those images were fully sized, front and center...
there actually hasn't been that many disruptive trolls.
there was a guy flooding votes and gay furry erotica across different accounts with a script, but he stopped once captchas and rate limiting were increased. wasn't really a serious attack either, just soebody having fun i think.
Making anti-troll mechanisms more specific than a captcha would be interesting. Make them paste sections of the FAQ in on login, like simcity did with the game manual on startup. "What is part b of rule 12", then make them "like" three posts that make the world better or be banned.
i'm working on code to expand images in-line right now, without having to leave the page to view image links. afterwards i could add a toggle to auto-expand images at one's own peril.
I'd rather have plain no images. People can post links to images if they want. Basically depends on whether you are trying to build a discussion site or a meme site though. I figure there's plenty of memes on reddit, but open discussion is dead there.