I feel like the new Chaos kits would look really good if you wanted an organic-looking sort of force. Like how the Blood Gorgons seemed to be, or something really twisted like how the Word Bearers could be.
Doesn't really fit the Night Lords. They're crazy, sure, but their fear-factor always seemed a bit more...deliberate. Not grown on, you know? Can't really see it working for the Iron Warriors or younger warbands either.