"O" I am sooo jealous. I got into model trains as an adult and went nutzo with them - HO. I did all kinds of dioramas - different from guys' trains, probably.
If I had a friend who had an orchard of trees, I would make a model of the orchard. I had a model airplane hangar for the one where my friend lived, plus his planes. All kinds of tiny cars and motorocycles to match those of my friends. A windsurfing scene and beach were in another part of the layout, because I liked someone who did that.
Had a NASA set up in one area, with all things space related. Some Matchbox matched scale, and all Hot Wheels trucks matched scale, tho cars didn't - had to buy Euro for the right scale cars. Had all the little people, even topless dancers for a strip club, lol. But I had priests, too.
Obviously had a Christmas village, lots of buildings - especially that funny kit-built one of the IRS building on fire, with flames and smoke. The Liberty Falls sets of houses, buildings and people fit scale and were reasonably priced each Xmas season.
Just about anything I did, or any business I represented, I had either a layout for it, or a box car. Eventually, it got so big that I went to N-scale for a smaller set-up. Then went down to micro so that my doll collection had its own train layout - that was fun.
But, I salivated over O and G-scale and shopped for years with my wish list in mind - just had to get the right house with the right garden for it. Umfortunately, it never happened and just remained a dream.
As I was trying to get a hobby business off the ground, doing 1:6 scale model doll accessories, my world fell apart - I gave my entire multi-$1000 worth of trains to a neighbor, plus some big toy trains for around the Xmas tree, plus the N's. They were put away for their little tiny grandchild (boy) to have some day.
Miss them like crazy.