I downloaded a track planning program, Railmodeller Pro, for my Mac and started playing with it. The train room in our new house (being built) is 10'9" x 20'4". These are the actual dimensions. I came up with this plan. The loop to loop at the top is an elevated line and uses O31 curves and switches.
The lower lines use O36 switches, O36 and O48 curves. I run traditional size trains so I'm OK with the tight curves. All suggestions and opinions are welcome.