Two ideas. Maybe some people would like only to draw or only to describe doodles. Though I don't know how this would affect the game. And a troll button for marking intentional chain-breakers. If enough people mark the troll then you could remove his image/description and recover the chain.

Some of my favorite (parts of) chains: http://i.imgur.com/52307.png http://i.imgur.com/SnT6r.png http://i.imgur.com/KhMql.png