I've had an idea that will barely take anytime or effort, but will improve the game enormously. On the settings page, a chance for a player to edit and create a map could appear. This could simply be a version of microsoft paint or something. The map screen can be edited by the user and viewed by other people. Another, even simpler, but slightly less effecttive way is that a player can make it on their own and upload it onto the website (like they do with a flag). It will get the same result, but be less convenient for the user.
This is like many other of the simple changes that have been proposed- national anthem, national leader, portrait of the leader. If admin concedes to this, then why not to the other suggestions? Each one increases the server load, requires new coding, and detracts from the features of NS2- which is where you are likely to see features like this.
Not to mention the fact that it would be a huge load on the sever. Do you really think that an entire online program doesn't take up a lot of space?!? Not to mention the fact that one picture for every nation would increase sever load greatly, the flag files have to be .jpg format and less than 6k to save space, the pictures your preposing would be measured in Meg!