I would say North America, Central America, and South America are all separate regions.
Europe I would split between Western, Eastern and Scandinavia.
Africa I would have North Africa and Black Africa.
Asia is the Middle East, Far East, south East, Steppes, and Indiana Subcontinent.
Australia and Oceania are the other two.
I believe the "brown box" is the fishing net in the process of being cast.The boat is in the upper left, yet there is some sort of brown box in the center of the tile. It makes me think of a wooden crab or lobster trap being thrown into the water. So I think it is crab, as some have suggested, or lobster.
Could be an indicator of what? It's just a red and white banner.
It's a red-white-red banner, which is a part of historic Austrian heraldry and is used as the flag today. The fact that they use it in the icon could mean that Austria is in, although it is doubtful.
Why would that mean Austria is in? The Civ in the picture being used is the Dutch, you can see their cities production. The selected unit is therefore Dutch.
The fact that the Great Admiral is modern ship icon makes me wonder if the icons can now change along with the art by era?