I did No-Face last year. I wanted it to be really big, instead of just wearing a sheet, so I made a frame out of wire and a PVC pipe. Without the sheet, it's sort of similar to an umbrella.
I didn't have a lot of time to do it, so as the day went on it got a little deformed, but I probably could have made it sturdier and the top completely round if I had enough time to weave more wire or make some sort of cap. The mask is just drawn on a board (+ purple paper) and was made on the morning of this con.
The whole thing is I think easily seven feet tall if held at full length.