A Japanese real estate site has a 1/500 scale model of a skyscraper free for the downloading. It looks good.
For your pulp science fiction games, here’s a paper model of a Flash Gordon style single seat speeder-flyer.
For fans of the wildly imaginative Miyazaki animated films, here’s a paper model of Howl’s Moving Castle. It might have some use in a fantasy or steampunk game; otherwise, it just looks like it would be fun to build.