I noticed when I tested the latest MG, that one scenario (one of the beginner ones) had an image in its folder. Curious what it was, I realized that it was an "override" for the background image displayed on the loading screen. In this case, it was simply used to show where the enemy camp was, so to make the game easier for the new player. I think GAE should impliment this feature, since it could be very useful for both purpose and for looks. For example, a tutorial might use it in a way similar to that MG scenario, or, more specifically, a campaign scenario such as Military's End of Morning series.
While it's not priority, the code to display background images for the loading screen already exists, and MG has done this already, should a reference be required. The usage is mostly visual, but does have some practical uses as mentioned above.