Masquerade mask with a leaf design is meant to be printed onto tulle. Symmetrical design except for the very center leaf.
Ribbon can be threaded through holes on a leaf on each edge of the mask to wear.
The full tutorial on how to do this can be found here.
(If you don't want to, or can't, print it yourself, I'm also selling completed masks in a variety of colors on Etsy.)
Designed in Tinkercad.