Frazetta artwork for Edgar Rice Burroughs' Edgar Rice Burroughs' Pellucida series, which is full of interesting ideas (and seemingly made for Frazetta) such as a hollow earth lit by a small sun inside--resulting in permanent nigh noon-- and crawling with dinosaurs and lizard men.
Art that was eventually used for the cover to the greatest fighting game of all time, the aptly named Match of the Millennium for the neo geo pocket color.