You know what piece of merch I just thought of that I would kill to have? A globe of the Avatar World? It would be both a physical map, showing features like mountain ranges and rivers and bays and deserts, etc, and a political map with names of nations, cities and towns. And it could even come with an accompanying mini-atlas (I do love expensive atlases...) with info on each town, city, nation, and geographic region/feature. Bryke have confirmed that the Avatar world is round, and this globe would have the benefit of clearing up the question of how large the ocean is that connects the map going from the eastern coast of the Earth Kingdom to the western coast of the Fire Nation.
Man, right now, this globe is at the top of my Avatar/Korra merch wishlist, even higher than a Pabu plush or a Blue Spirit & Amon mask combo pack.
I'm seconding this globe thing.
Whether or not the Avatar'verse was round was something I got to ask Bryke at Comic Con this year. I figured they're asked all kinds of geeky questions, but still felt the need to apologize for mine being geographic in nature. Brian looked at me, and said: Well yeah, of course. And then went on to site proof from the show. It was the best geeky answer to a geeky question.
So yeah, totally a globe.