I'm not even a huge fan of Chaos and I agree with you. Thousand Sons helms are wicked cool. But, I'm sure they will be an option for customization down the road. Or, at least I hope they will be.
Chaos (Slannesh) was my first army and I too am a fan of the downturned horns. I do like the 'sans horns' look as well as the topknot look.
Looks night lordish, I like that, I don't know if it was intended but those wings on helmet are a obvious hint for me. oh man, I support the chaos way of making things bigger beyond any reason, but this is an overkill