The original sketch is up for sale if you want to jump into the bidding war. Link below.
Frank Mentzer said:
Initial cover concepts were similar to the previous edition, portraying a group of adventurers with a dragon. That was almost used, but it bothered Gary. After the color images were ready to be finalized in oils, after a lot of plans were made, Gary changed course. He asked Larry to focus the action on just one fighter and one dragon...