Pack up some leaves
During the fall, pack yourself a couple of baggies of fully dried crunched leaves, and pine or cedar needles. Then you'll have them when needed for your fall display. I used crunched up leaves and needles as ground cover around Steen's Maple House on the top shelf of my display.

City Streets and Sidewalks
As far as the thin sheet of plastic on the white "Home Depot" styrofoam goes, I have painted it in a light gray. Then carefully peeled it off the styrofoam. This makes a great 'sidewalk' that can be laid down on other pieces of styrofoam. I use straight pins to secure it. Then I pick it up, roll it for storage, and use it again next year. You must be very careful to peel the plastic off the stryofoam slowly, because it will tear if you go to fast. Painted black it also makes "streets". (Patsy)