I am freelancing in terms of road names, at least. I run the rolling stock I have, which is all over the place. Well, it is all North American, I suppose. Just turned out that way, since most of what was available to me as a kid was North American.
As for the layout scene -- it is small town America. A bit dated and run down, like a lot of small towns are today.
But the vehicles are what set the time, really. I have a thing for air-cooled Volkswagens, especially Bay Window (1970's-era) buses. One of my other hobbies is restoring those buses, and I have owned about 16 of them over the years. So, most vehicles on the layout are buses (including panel vans and my favorites: pickups), most non-buses are the many varieties of air-cooled VWs -- bug, squareback, notchback, fastback, etc. I even have a VW dealership in the works (Walthers car repair place). I've got campers in the campground, and other cars and buses around town.
But I am not stuck on making it all coherent. I have a modern New Mexico RailRunner on the tracks, so that would not be 1970s, of course.
I'm just having fun.
Some of you may find this amusing: Having a geology background, I have been much more concerned about having a coherent geological history of the layout, evidenced by rocks seen in outcroppings, than I have about the railroad. You can't just have a light-colored rock here at one angle and a dark one over there at another angle. Are these part of a transgressive sequence from the mesozoic? Limestones to shales to sandstones? How about faults? How about a really big fault that exposes some uplifted metamorphics? Ahh! It's too much! I hate to admit it, but getting the geology right has become a hurdle to my scenery work! I just need to move past it and have a rock here and there...