I would definitely like to see more blankets. The ones included in Jungle Adventure are among my favorites and I use them often; in fact, that was one of the things that helped sell me on that pack since the designs are great and fit many styles and uses. I also have used the baskets from that pack. These are small and simple things but they end up becoming very useful and intrinsic, and having a new pack or kit with that variety to represent more cultures would be really appreciated. If decorative, great, but if craftable, even better. Think about also how additional woodworking objects could be added, such as additional decorations and furniture in traditional styles. Also, the recipes. Perhaps additional craftable medicines. And new stories that could be told. These are such minor things but they matter! That's part of the reason why I would lean more towards a smaller Game Pack or Kit rather than an Expansion Pack, because if it were a larger expansion there might be more pressure to create a full world, etc. when what would be most interesting would be gameplay, CAS, and BB. I feel like we have great worlds where Native cultures already fit naturally and we shouldn't be in a situation where they have to feel like they 'belong' in a specific world that gets created for them, but rather that they are already everywhere, just waiting to be incorporated into the game. Naturally, if people want to use specific existing worlds, there is a lot with Horse Ranch, StrangerVille, and Oasis Springs that fits into more of the desert / western-style locations, while more neutral greener worlds fit many other traditional places if rebuilt.
That said, if it would be an Expansion Pack and there were going to be a new world, I think something representative of the Great Plains of the US and Canada might be good (think also of including a new National Park), or alternatively, a very forested world like found in the Pacific Northwest of Canada. We haven't gotten those yet and they would also build off the Natural Living skill from Enchanted by Nature since those would be good places to use those skills based on environment (lots of harvestables, etc.). Because I suspect Maxis would not want to have exact representations of various tribes and nations, but rather something which is broadly representative while being respectful and inclusive (again, like Snowy Escape and Japan), thinking about worlds and environments which are not tied to just one Native group, but are instead places we haven't seen yet, would be the best approach given the company's sensibilities with cultural depictions. The one exception that I would perhaps make and think could be requested, though, would be if the world would depict historical built aspects of a culture that remain today, such as a place reminiscent of Chaco Canyon, or the Cahokia Mounds, or even much older pre-historic sites such as the Lascaux Cave Paintings in France. These could be included, again as National Parks or places where outdoor museums are located (this would be a new idea we haven't seen yet), and connect the ancient past to the present as modern Sims represent and maintain the cultural sites. I feel like if something that significant were to be included, it probably would have to be an Expansion Pack, or at least, a Game Pack with the level of complexity of Jungle Adventure. I feel like all of these things would have such broad appeal that many players would be interested.