Peter Dahmen, pop up paper sculptures.
Various paper mask templates, made for but seems to print out far enough from the top/bottom to do on okay at least for the skull.
Papercraft panda head printable DIY template 6 by WastePaperHead
Bull Mask - Build your own from recycled card
30 Interesting and Creative Brochure Designs
DIY Geometric Masks for Halloween by Steve Wintercroft