What Matt, Bill and Melgar have said also applies to me and my layout. So far, I bend the rules; put in or keep something on the layout that I like, but which has nothing to do with my theme (The Put); and what I do have on the layout resembling a feature of the Put is not a scale model, but rather a caricature, of something related to The Put.
This is illustrated by the video below:
The engine pulling this short freight train is kinda like, but not exactly like, what might have run on The Put.
The HO buildings the background are very nice models but, to my knowledge, are not like any buildings along, or in the vicinity of, The Put right of way. Since I like these buildings a lot, I choose to keep them on my layout, at least for the time being.
However, it is very possible that my layout will continue to evolve in a way that more features of The Put will be added over time. Arnold