I think three flags are more impressive for presentation than just a single one
So I chose one for the board as common element (you recognized it correctly)
One for the country (which the user is affiliated most, i.e. most his/her nationality)
And the third one for the state: e.g. the US consists of several states (Florida, Texas, California, etc.), also like e.g. Germany (Baden-Württemberg, Bayern, Hessen, Sachsen, etc.) ... or a flag a user feels also associated him-/herself (e.g. state of birth, European community, candiland
) ... or in case the members does not prefer another country, just a dummy flag like the one above with the Playmobil logo.
