Here is a very interesting conceptual illustration from the development of the season one He-Man episode "The Curse of the Spellstone". This illustration is one of the earliest designs of the Fire People, the tribe of warriors that guard the Spellstone. Many ideas were illustrated until Filmation settled on a transparent group of characters that bore no resemblance to this design. Since this design was abandoned, this illustration would make for a pretty interesting character on its own! Fire-Man, anyone?
(click on the image to see it at full-size)