Taking the risk to make myself unpopular but here is a wish from the heart.

Discourage/ban all nationalism. Especially flags.

Reasons:
Nation-states and country borders are a fairly recent invention in history. In this time and age, it's quite counter-intuitive to still keep identifying oneself with (or get emotionally attached to) such divisive concepts that have been devised by those who govern. Especially in a game like this where collaboration is encouraged regardless of anyone's location or belief, we should not get counter-productive over flags and the politics associated with them, or get to argue wether flags represent government entities or the people (they are usually owned by the former, just to say).

Further, I find flags (and also logos) are just so utterly uncreative things to draw. To me, it just shows how societies are still immature; false attachment to the divisive and competitive concepts they were raised to believe in, to the benefit of those who profit from divisiveness and competitiveness. Therefore, please consider a ban on all flags and instead encourage "real" artwork (especially original one).

e: For those who still want to display some honorary mention of their ethnicity/people/heritage, there is likely plenty of symbolism available which may suit their case much better than a symbol of nationalism.