Clifford Button of Paper Tiger Armanents offers a free 1/72 scale brick structure. It was inspired by a building in the Strand district in Galveston, Texas.
Here’s a tutorial / demonstration on making a nice looking bombed out building.
TerraGenesis has a nice illustrated article on making 28mm scale European buildings for your World War II games.
This paper model is an appropriately grungy model of an auto electronics store.
Terragenesis offers a great photo tutorial for making medieval wargames buildings.