I have some of these and similar products. I mount them to acid-free mat board (not cheap, but worth it), and then use a gray artist marker to darken the edges of the mat board, e.g. "Basic gray 6" (http://www.dickblick.com/products/blick-studio-markers) The thick mat board and markers add depth and I layer the building flats on top of photo backdrops. i'm very pleased with the result.
You can experiment with the N scale products on an HO layout (for example) to get some forced perspective, too. At this price, you can afford some experimentation :-)
I for one will say these are some of the greatest products ever! The pictures above don't do them justice. I've seen them on a couple of layouts now, including Harsco's layout, and they are incredible. You almost have to touch them to realize that they aren't 3D!