Here is a modular layout for Andy, a forum member, designed to fit in one of his garage stalls. Its an 8X14 space, and Andy wants the design to be modular in case he moves in the next couple of years. The modules are based on a 2X6 footprint, but you can see that only two of the modules adhere to that exact size, but this general size will be easy to disassemble and move when the time comes.
Andy wanted to use Atlas-O track, with an O-72 outer loop. The inside loop is O-63, with #5 cross-overs connecting the mainlines. There is a siding and engine storage track that is O-72 with O-72 turnouts. The rest of the turnouts are O-54, limiting locomotives and cars to that minimum diameter once off the O-72 mainline and storage tracks.
Access is through two 32" lift-out bridges, leading into a comfortable operating space. There is a small yard, and a number of industries to be serviced, a large station at the left, and a smaller below. Comments and suggestions are most welcome!