Here is my Christmas Day efforts, pieced in pink foam, with a creekbed cut through and the basic track layout. Simple HO scale flextrack, with every other tie removed. Trying to make this as simple and basic as possible, the idea that ANYONE can do something similar, no special materials, tools, etc, just a little space and a desire to try it all.
The "West End", the Bachmann gas mechanical is about the perfect size for this, although I have a couple of similarily small, 4 wheel, short wheel base Milwaukee locomotives in mind as well.
The curve in the center is some of my usual smart-ass efforts, one of the "suggestions" for track for the Gold Spike is a crossing, which of course would be of zero use here, so I added one anyways, conceptually this is the camp foreman's office and a speeder or small railbus pulls up to the office with new employees.
The "East End" of things.