Ben Affleck's hit movie Argo owes everything to a movie called Lord of Light, an adaptation of a Roger Zelazny novel. Lord of Light sat in development hell until CIA operative Tony Mendez renamed it Argo and used this insane scifi movie as a cover story to smuggle 6 Americans home from Iran.
Part of Mendez's plan included getting concept art, tons of it. So Mendez and his crew hired legendary comic book artist Jack Kirby. Thanks to the Lord of Light website and Buzzfeed we now have a high-res look at the insane storyboards of what Lord of Light could have been if it weren't just a CIA conspiracy. The ornate helicopter landing pad alone is worth a revisit!
Science Fiction Land Plus, right now there's a kickstarter-funded documentary called Science Fiction Land which has a lot more information on the lost project.