If you are using foamboard for walls, you can just draw lines to give them that segmented look. Depends on what the use is for. Like, if you wanted a stark white Cloud City (Empire Strikes Back), you can draw the lines with a marker. That's the old Luke Ellison technique too.

I've painted the foamboard a drab gray and added the lines too for a more metallic look. *shrug*

Email me at SunCe4@gmail.com if you want my dios to see what I've done.