I made the statement previously that a great place to start planning a layout is to pick the footprint and then design a track plan from there.  The layout footprint will answer if you have room for things with a little thought.  Here is where I ended up.  As it turns out the finished basement room is about the same size as the paper the diagram is on 20' by 15'.  I could have (in theory) used the entire space...

It was June 2013, I stood in a cool and inviting finished basement of my new-to-me home. It felt wonderful, my wife and I more or less finished moving in and I was thinking about what to do with my new basement.  Looking back, I am not sure if this was a major accomplishment since we did not actually furnish every room for another 7 years.  The basement had all the makings of a train room (carpet, drop ceilings, lights, outlets, and buy in from my spouse).  I was going to have a layout.  Years later this would be one of my favorite photos.