I like it as well. It'd be pretty cool to see those floating around in Multiplayer. I mean, the more options we have, the more customability and individuality, right? And I'd agree that it is the helmet from the Bungie Day painting. Whether it's actually in the game or not, it's nice to see it with textures and such.
I think it looks awesome. What'd really be funny would be to see a completely black ninja or cobra styled costume (whichever it was) hiding in the shadows. A CQB walks by, and the Ninja (for this instances sake) strikes, assassinating the CQB.. ninja style!