First, a picture. This is my "Strumpet Brewery." It's the Walthers "Arrowhead Ale" background building. I painted it a brick red, and added my own decals. Note that this particular structure is really very generic. You could change the signs and it would become a Buster Brown Shoe factory. It's also only about an inch-and-a-half deep, so it's made for the back wall of your layout.
But, my layout doesn't have a back wall, so I added an interior and made it a "sliced off" building instead:
As for a separate "Structures" forum? I don't know. Personally, I'm glad they created the Electronics and DCC forum, because that really was very distinct, and didn't mesh well with "Layouts." Structures, on the other hand, are really very integrated into "Scenery." But, if we pulled "Scenery" out of "Layouts," what would be left? Benchwork? Trackwork? Yeah, but are either of those enough to stand by themselves?
It takes an iron man to play with a toy iron horse.
Large brick kits and walls may work best. For each building on a backdrop you need a front and two sides. (Plain styrene can be used for the roofs.) Vary the height, length, width, depth, and color of each building. Then line them up next to each other.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.