It's cold here in Ohio in the winter, my OO equipment has only just started to arrive, so I had some time to play with this.
We did have paper buildings here in the US when I was a kid, but I have not seen any in years. Metcalfe kits look pretty neat, but I'd have to order them from Canada. So..I thought I might try to make some of my own.
The brick and stone textures I found online, but they have been mangled alot. All the rest is my effort . I followed some photos of English towers. I found online.
The really neat thing is, (We would call this an interlocking tower here) Is that this tower could be dropped anywhere on the NKP (in the steam era anyhow) and pretty much fit right in! It's pretty close to a tower that used to stand about a half-mile from my house.

It's buildable, I'm looking at two of them I just finished right now. Just takes some carefull work. Stairs will come later.