In another thread I suggested 10 worlds, 1 tutorial area, 1 hub and 1 finale area like Furnace of Fun
1. Jungle Falls, as shown in the pictures it will be jungle themed with weird islands and waterfalls. Expansions can lead to more watery parts or deep into jungle ruins.
2. Western level. I can't recall how many times Western levels were dropped in Rare games, particularly CBFD and Nuts N Bolts. Expansions could lead to buildings like saloons or deep into the desert to mesas or bandit campgrounds.
3. Someone suggested B-Movies and a Theater level instantly clicked. You can go to a concession stand to get food for characters, climb on top of the large signs outside of the building, and best of all go into the projector room and switch film reels to enter different genre mini-worlds: Horror/Scifi (a B-Movie alien flick), Romance/Drama (sepiatone Casablanca-esque runway), Action/Crime (some city with a lot of cars whizzing by and explosions), and Comedy/Musical (maybe taking place on a stage with various switching stage props and backgrounds like the Gloria level in Psychonauts and hop around on giant instruments above the stage like drums to bounce off of or piano slides, just other musical things that would be coll and fun to do) (Edit: saw someone actually said something like this on the second page, oops!)
4. Haunted Forest. Fills both the horror and forest world types that I feel are both needed in these types of games. This would expand into spooky trails that might lead to creepy abandoned tunnels, hidden forest graveyards in the middle of the woods, scary gnarled trees, creepy cabins, you name it. I'm mainly thinking of those creepy death forests and stuff in Japan you always here about and see in video games or videos with alleged ghosts in them.
5. Eastern Culture world. Playtonic and Rare never really went with this theme in any of their games and it's probably time they did. I chose Eastern Culture instead of specific places like China/Japan because a lot of worlds in games that do use this theme often just go for blends of ancient and modern eastern culture instead of strictly China or Japan. This could expand with pagoda buildings, lines with lanterns on them you can grind on, a Great Wall looking area, potential to jump into stuff like anime or Godzilla/giant monster references or areas, etc.
6. Steampunk/victorian world. A lot of pipes that can lead to secret areas, mech-like machinery to either fight against or jump into, victorian buildings to explore, etc.
7. People mentioned a snowglobe world and I feel that that might be the best way to bring back a snow level without treading already explored themes. This could expand to Rankin/Bass-esque areas to get pagies in like a toy factory with giant toys you can fight again, igloos, ice caverns with monsters in them, cold cabins that someone might be stuck in that you can dig out, etc.
8. Someone mentioned a carnival level, and that sounds good. It doesn't have to be haunted per se, so maybe instead a Disneyland style of overly trying to satisfy guests and brush away glaring problems? "Welcome to the knife throw! Carnival staff are not responsible for injuries due to the waiver you signed at the front of the park! ENJOY!". Also, not to mention attractions you can expand into like a tunnel of love, a fun house with mirrors, a freak show where you can help the people in there with stuff like pulling a sword out of a sword swallower or something, a dunk tank you have to throw something to activate, etc., and finally a big top with actual big top stuff this time, such as elephants and daredevils on bikes in round cages etc.
9. My other idea plays off the fantasy mountain someone mentioned before that you have to climb up and there's dungeons and caves and monsters you have to explore and fight through, maybe at some point coming across people that need saving. At the top of the mountain is a castle that belongs to an evil sorcerer or sorceress that you need to fight, who has other rooms in the castle like a library where you climb up bookcases or an evil thorny garden.
10. Forgot a water level.... How about an aquatic supervillain lair that's underwater? Like, it can take place on an island that has an aboveground villa and maybe a volcano on the side of it that you can enter, and when you go into the villa there's an elevator down to a secret underwater base with various traps and baddies to avoid? You can save secret agents in death traps, use lasers to open cages, and have to escape a tank full of sharks! Also, there's a large tanker above water filled with jewels that you can run around on, and maybe also a submarine docked to the aquatic base.
As for the final area, I'm kind of drawing a blank. It kind of depends on the villain, which we don't know of yet. However, for the tutorial area I really hope it's an inverse Spiral Mountain. Like, maybe instead of going UP a Spiral Mountain, one day our heroes are relaxing at home and a great spiraling tunnel gets drilled into the middle of the plains going downward, like a Spiral Chasm.