Peter pan theme costume ideas?

I just finished reading Peter Pan last week, There are not many more carachters other than the obvious ones but... There is Nana, who is a dog but you could make it interesting, like a cat costume? I cant think of anything abstract from the book that you could be. Peter pans shadow seperates from him at the begining of the book, could you be a shadow? There are mermaids too. Sorry I can't help more, its quite a simple childrens book so not many people in it.