Maybe paper model building facades would work? Don't think I often see them in 1:18 scale, but they could be scaled up if the resolution's high enough. Could also just print the building front. May have to split the image across multiple sheets of paper for 1:18 scale. I know the model railroad and 1:25 scale car guys make paper models.
This came from
http://papermau.blogspot.com.br/ 