I saw this in Spain a couple of years ago and vowed I would do it at the next fancy dress party I go to.
You go as a Picture!
This bloke had an old picture frame with a sheet in it and his jacket sewn into the sheet, he had a silly beard and sailors hat and a big pipe and would just go and stand against walls, it looked mint. I'm sure I have a photo of him, will try and find it.
That sounds cool; if you can find a photo that would good to see it.