I'm installing backdrops around "the other end" of the layout, a total of about 20 feet, although much of it is under shelves and not so tall.
The big area, though, is that shown below. Its five and a half feet by two and one half high, right behind the layout and very visible, and now just wall covered with acoustic tile.
One good thing is that I can get at one end of that wall from the aisle on the other side of the layout, as you here.
I installed a six foot long alum U-channel at the bottom as kind of a sliding channel for my backdrop . . .
The backdrop is foamboard cut to fit.
I painted it light blue (latex, using a small, short-nap roller) and once that had dried, then some painted clouds on it . . .
Here it is installed, with a nice oak retaining frame installed on the left edge. Even with the seam between the two panels showing (I will hide it eventually) it is a monster improvement.
Next step: paint some distant mountains, closer hills in the background down low.
then attache some building fronts.