If you constantly check Thingiverse for new things to build on your 3D printer, you may have seen the Mad Max: Fury Road mask. If you haven’t, here it is.
CarryTheWhat says you can print this in once go, but you are going to need a lot of supports to get this to print without falling apart. I know I can get this to run on my MakerBot Replicator 2, but if you have a small printer (sorry @coverville), you may need to find software that will allow you to break this into smaller pieces for gluing together later.
With the proliferation of 3D printers, and the continued reduction in price, I expect to see more and more costumes incorporate 3D printed elements in the future.