I had some ideas for planes/sets that would probably not get used for one reason or another.
A long time ago, <Overarching Villain> betrayed three former allies and imprisoned them on different planes. <Heroes> seek out these planes to find out why <OV> would imprison these folk (and also why <OV> didn't just kill them).
Plane 1: Iquatana - the Psychedelic water world. The mana here is trippy and overexposure over an extended period can cause severe addiction with harsh withdrawal symptoms. This addiction was the means by which <OV> trapped the PW here. Four major races are Cephalid (WuB), Homarid (GuR), Merfolk (GWu) and Surrakar (uBR, sometimes I switch them out with Amphin Salamanders). Yeah, I end up putting a few flyers with "~ can only block creatures with flying." Mechanically, I had the set as a hybrid set with adamant and sunburst as returning mechanics.
Plane 2: "Puzzle world" - A long time ago, a long lost planeswalker set up plane to be a mental prison world for the worst of the worst offenders who couldn't be easily contained on their home planes. The plane self regulates through a clockwork like perpetual machine with no intelligent oversight. Minds are tethered through an interplanar connection to essentially a meat puppet, leaving the true body in a bit of a comatose state on the home plane. When that puppet is destroyed, the mental link is captured by the central machine and automatically tethered to a newly produced puppet. To prevent prisoner "escape," the plane is designed to be overly mentally taxing with an aesthetic mix of Escher, Wonderland, and a sanitized version of the Saw movies. Imagine all food grows in a shifting hedge maze, and the fruit from the tree in the middle has a Rubik's cube like peel (only the puzzle is different for each fruit). The method to release people is written somewhere on the plane itself despite the rest of the multiverse forgetting all about it, but the ritual would need to happen on the prisoners' real bodies on their home planes. If a planeswalker dies on the plane, they will get trapped in the plane's puppet cycle in a body that most likely doesn't have a spark. Initial thought was Suspend as a returning mechanic, but the was the "set" I worked on least mechanically.
Plane 3: "Empty Post Apocalyptic" The world had once been under a Phyrexian invasion. In desperation, the people of the plane decided to blow up the plane, protecting themselves by going into stasis machine meant to counteract Phyrexian infection. The plan worked, but the stasis machines were programmed to reinforce the idea that you need to counter the infection. So when the people woke up out of stasis, there was a lingering fear of infection. Eventually, the paranoia grew and the new social groups fell apart. They ended up sticking everyone back into stasis. The cycle would repeat, but grow faster and faster in between cycles. Now anyone almost immediately goes straight back into stasis. This has left the world to overgrow the ruins with no sapient species left to push back. However, the documents describing the Phyrexian threat still return, leaving an unsettling feeling in the air. The set would be an extremely low creature count, but a high amount of "spell morph" to fill out the needs for creatures (The flavor these "spell morphs" would be false alert jump scares, like a creaking door.).
In terms of an Americana set, there's actually a couple of states that might actually have enough to them that they could hold up a world on their own. The main ones that come to mind are New York, California and Alabama. Unfortunately, there's a lot of states that wouldn't have the full extent of required geography, but these are a few of the ones that do.
California speaks for itself, but when thinking about New York, people tend to focus on NYC, but the upstate also has a lot going on as well. It has natural beauty in the Adirondacks, Catskills, Hudson Valley and Niagara Falls that's a bit underrated.
Alabama tends to get pigeon holed into a very particular part of history, but it probably has one of the largest varied swaths of American history of any state. It's important for proto-Indians; the conquistador era (the start of the downfall of the de Soto expedition);
French, British and Spanish colonial claims-War of 1812; the Trail of Tears; the Civil War (
This map being a particular reason to point out Alabama. Even then, the map isn't giving the full extent of the divide as there were some delegates who changed votes at the end for political positioning purposes.
paper); Reconstruction; Civil Rights Era; the Space Race, etc. It's just a state that has
weird layers of intersecting history beats all over the place, (plus random stuff you might not expect, like Helen Keller, underwater forests or weather events like Mobile Bay jubilees).
In terms of other places for inspiration, I hate how people tend to lump the Inca in with the Aztecs when the architecture and clothing are quite noticeably different. Plus, I'd like to see a
quipu writing system in a setting.
Another one I'd like to see for architecture reasons (though, there's a lot more to it than just that) is the Aksumite Empire/Ethiopia.