I think this rule would be tricky. Ultimately, it'd just exist to stop trolls from trolling, but where would you draw the line? Sometimes non-trolly people occasionally use images/memes that are genuinely funny. Would they be banned from using images too? What if somebody had a legitimate reason for posting images, like a post saying, "I am an aspiring artist and this is a picture I drew for a friend on the site." Should they not be allowed to post images?
Most people wouldn't want that, but then if people who post occasional funny images or their own artwork are allowed, you get trolls going "How come they're allowed to post pictures and not me?" Then when you explain to the troll that people are only allowed to post images in moderation, and only if it's relevant to the thread, then you get a troll who's still posting images, but now adding explanations as to why the image is relevant, or starting new threads going "I'm an artist too and this is just a little scribble that I doodled today." ... With a picture of the Mona Lisa.
So to sum up... Can't we just ban trolls from trolling instead?