Just a quick DIY cosplay I did in the picture.

Thinking of cosplaying Lucy from Elfen Lied next.
Problem: Lucy's helmet. I can make the vectors/hands to attach to my back, but the helmet is my main beef. How would I make it? I'm only doing half the helmet like in the promotional posters, but what material should I use? I'm looking for something lightweight and easy to smooth out so that it wasn't rough.

Also, do you think I could pull off Lucy's look? I tend to have more of a JHorror ghost type look and I'm looking to go for something new instead of a cosplay like Enma Ai from Jigoku Shoujo.

/total newb; please be gentle