however, with that being said, most 3d editors allow you to make most models 2-sided, and with the way his models are set up, its quite easy to create (OR... flip the faces and double your obj or FBX, with one texture set for the outward facing, and 1 texture set for the inward facing.
...or I could just reuse all the wall models and pretend I made new one =) I would make props for the rooms of course
I think I may have misunderstood the original request, not to reveal a model that's onesided, but to have decorations for the internal of a model..
But, to answer. What I really like is that Keith already took care of that with all sorts of little wooden beams and such for his Modular village, so that an AssetForger (yes, I'm coining that as a term now) could easily add baseboards, half wall panels even articulate walls inside. He can even use some of those panels for other things like wall bookshelves and more. Scaling, rotating and moving the various blocks to fit certain ideas can really make the blocks sizzle, without a huge Poly boost.