After having done the Sebian & Montenegro flags I was saying to a friend "shall I already make flags for Flanders, Wallonia and Brussels?"
(there are three regions, not two, unlike what some Flemish politicals say)
I may indeed add flags.
I could add flags for many other sub-country entities. Like US states.
In the flags set from www.famfamfam.com there were flags for Scotland, England and Wales, I made the EU, DDR, Quebec, Serbia, Montenegro and few others, but it is not easy to make them in the same style as the original ones.