Yes, building material. Have you ever thought of that? What characters use to build their homes with can say a lot about their financial class, race, personality, culture, etc.

So,

what are houses in rural areas made with?

What are buildings in the city made with?

Do buildings have glass windows? If yes, what kinds of buildings are they?

What are the roads made out of? Mud-packed road, concrete, asphalt, tile, etc.

Is there any kind of material that displays wealth?