TinkerCAD is free, web-based modeling software that allows you to easily create your own models and export .stl files for printing. It's even easy enough for elementary-aged students! Maybe something for Printer Chat?
The Microscape is a really cool art-mural of a city. You can purchase a printed ‘square plot of the city’ to give your mantelpiece a cool, kitschy touch, or go ahead and purchase adjacent plots to make a crazy mural of your metropolitan city.