Painting the sides of the facades was my first idea...but in fact the building facades in question are very close to the viewer's perspective and form a background along two long runs in my basement, and these areas are cantilevered wall extensions, one of which is about 20" deep and the other is only 15" deep, thus having decent detail on the sides of those facades that sit on the ends is what prompted this inquiry. The picture above shows the façade background on the 20" extension. The left-most façade has a black side that gives it away as a façade. A little brick detail here would go a long way, I think.
Example of a façade with black side that IMO would benefit from brick effect:
