I’ve got a special place on my layout that I’m going to use to place a large mirror to make the layout look extended.
On some layouts, a skillfully placed mirror in a valley of trees or on the end of a street or by a spur can make your layout look bigger than it is and can even fool visitors
trick is to angle the mirror so visitors can’t see themselves.
Also, you would not want to see passing trains in the mirror. However, a mirror at the end of a spur or yard actually works even when trains are moving.
I would encourage you to take a small hand-held mirror and walk around your layout with it, turning it in different directions and seeing if you can pull this off