Base idea

If I'm not entirely misreading your post, what you're asking for is Dev based and not necessarily player based, as far as your idea is concerned. That being the case, the chances of something like that happening are going to be slim to none for some time, considering we just got the ability to 'free stack/rotate' (not be tethered to the floor safe/floor tile only method) and the new 6-location teleporters. That's really been the only base building upgrades we've had since bases and base editing entered the game.

However, there are some absolutely amazing base builders on the boards and in the game, and I've seen them come up with things like apartment complexes, or entire mansions for their bases. I know creating a 'night time' setting is fairly simple to do. Making second (and even third) floor buildings is just a matter of stacking things the right way until you get the desired effect. I've seen a combination of stacked desks and SG wall banners used to make the appearance of an elevator (you side step from one room and into another, like a secret passage way almost), but the idea of a true elevator effect like a lot of our missions isn't in the programming.

But, I fully support the idea of new wall, floor, and ceiling textures. I'd love the ability to throw a city scape on the walls of my base and build a skyscraper effect, or a forest, or any number of other 'atmospheres' than what we already have (which isn't much).