My suggestion would be to add a button to let you choose from a list of wallpapers including the old one (and any new ones you come up with).

I prefer something that helps immerse me in the game world (like the old one did) instead of pull me out of the game, remind me I am playing a game, and creates an accosiation between the commonly scene shot of ESD and the game's corporate logo that comes to mind and pulls me out of the game every time I enter ESD system.