We want to have the background image change dynamically based on where the player currently is. We would use a pool of predefined background textures that represent various environments (forest, city, night elvish, taurenish). Then for newer zone (WoD and after) we could use the animated multi-layered background from the mission tables (like what Console Port's dev did in his custom Storyline skin). We need a nice default fallback (nicer than the stretched out night elf loading screen texture) for when we don't have manually defined textures for a specific zone.