I have built a couple of houses, one a ruin. i have gone for an adobe/desert vibe, inspired by images like these:
https://houseofqueeg.wordpress.com/2012/09/03/28mm-afghanistan-skirmish-wargaming-terrain-board/
http://www.tabletop-terrain.com/archives/2007/07/12/800/cairo-table-for-luggage-lost/
For one thing, a flat roof allows players to put models on them. I intend to build a small village, but for now, here are two isolated buildings: