Hi Erin. For a really big map (say, just smaller than your door), what comes to mind is the brown paper rolls sold at Lowes/Home Depot for paining projects, although heavy package wrapping paper would probably work also. Then just lighten it, but not completely covering it a solid color anywhere, with the 97 cent flat white spraypaint from the same stores. This is largely to lighten the brown a bit to more of a parchment look so that it is not quite so dark and allow your markings to stand out better. Use markers or paint to create your map...perhaps customizing it to match your haunt layout. Then burn the edges (small sections at a time so you can control the amount of burn) so that the edges are not straight and look old. Tearing may work also if you don't want to mess with the flame. Lastly, when you're happy with the look, spray a couple coats of some type of flat or satin clear sealer (no gloss) over the front and back for water resistance. It probably would not be completely waterproof, but may hold up for several rains if using doublestick tape to keep the wind from getting behind it.
I think this should work but haven't tried it. If you think this would be of interest to you, I have all the items I listed and could do a square foot sample to see how it works and holds up to being sprinkled with a hose. Just PM me if interested and I can try it this weekend and post the results.
