For their Mars Attacks game, Mantic released sets of 20th century style brick ruins. They’re good looking, but with a little work can be even better.
Mantic
Kings of War II
Mantic’s Kings of War, Second Edition is now available as a free download. There are also several free Army Books.
I can’t help but thinking that this game is the successor to Warhammer Fantasy, which Games Workshop has essentially abandoned.