Start simple and add things slowly over time. Running a good heavy accessory bus wire system now, should pay off long term for adding things IMO.
Being on a shelf up high can limit visability. Consider running right on the edge with a plexi/lexan or wire fence for the rare derailment. Open areas of plexi shelving is pretty cool too. I used a Rubbermaid steel rod laundry shelf similarly as well; deep to the wall for enough room to use a few full sized buildings vs just flats on the wall (flats being only the face of buildings)
Street lamps add some real ambience if you tend to dim lights when the pace, mood, or customer traffic is slower; or have a darker stretch of ceiling. (rope lights and "gutter lighting" as well.(a long sconce)
A net search of plexiglass, ceiling, & model trains brings up some cool examples. Other key words like , hanging, mounted, shelf layout, and fence change it up some.
