I know it can be done in sections on a printer, then pieced together. One of the FReepers at a DC Rally had done so with a picture of Reagan. It was great!
I suggest we use that corrugated plactic sign material for strength. They could then be covered with a clear kitchen plastic. There is also a clear plastic in larger/wider rolls used for wrapping stacks of cartons on pallets that cwould be perfect for that.
I'll check into all that today.