Here are the nails I wore a few weeks ago when I went to see Thor: The Dark World. I'm not entirely happy with them, I think Loki's helmet looks ok, but I'm not even sure that you can tell what Thor's helmet is supposed to be. I used these nails I found as inspiration, you should check them out, very cool Loki nails! Although I didn't want to do just Loki nails, so I also used a photo from this page of Thor's helmet (this page is actually about a nebula, it's awesome!). 
The colours I used here were Chine Glaze Man Hunt, Starboard, and  Barry M Silver Foil, Gold Foil. I used W7 Black for the outlines of the helmets, and topped everything off with China Glaze Fast Forward.
The Barry M's were a right bish to do a gradient with, it took ages to get them to look like this. Goddamn one coaters!