GFIV,
Did that years back for a Christmas display layout. I used old Lionel O27 tubular, Gargraves, Atlas and RealTrax. It also had Bachmann HO for an ON30 loop, Atlas HO for a trolley back and forth and Kato N for a park ride. It was a series of loops that did not have turn outs.
6 O gauge, 2 On30, and 1 N gauge. Stopped putting it up when we redecorated the kitchen.
While size has its own quality, hopefully my scenicing skills have improved.