These can appeal to an audience of inspiring game developers since it shows environments that were there and how they molded some part of the game to give the developer how to create a character, elements or scenary in their game, thats why releasing concept art is very important since it can give sight of what the game would look like before release
And it would provide a look in for what the games would have looked like in promotional art when people pre-ordered the game which could also keep the history in game design for other people to use when in courses too, like me.
How these could be used for creative media.
In each of the concept arts there is an environment that was never used, they could be combined to create a wallpaper for collecters if they pre order a game, in the deus ex there are 3 mechanical arms which could be used as a figurine, and the character preproduction could also be used to create a book about the game before it was finished, or as in spelunky's creator derek yu you could create the concept behind the game and how it formed gameplay difficulty etc.