An icy moon. A planet of giant trees that tower above the loamy earth. A tropical paradise planet. Archetypical worlds often are created by amplifying a single geographical or natural element and allowing it to completely dominate the landscape. Worlds created in this manner are common in most genres of fiction, as they can be used to quickly generate fantastic but still relatable settings. Consider using an archetype as a base and then layering additional elements or other biomes on top to create more nuance and realism. Archetypal worlds are also often combined, such as a jungle world with expansive subterranean caverns.
For some reason (miasma, predatory creatures, magic, etc) the bulk of humanity exists in high altitude regions or on flying or floating vehicles or creatures. Levitating fortresses, airships, or domesticated drakes may be common means of transport.
Land consists of a series of islands (often tropical but not necessarily) of various sizes. Travel between these landmasses often depends on ships, planes, or blimps, and pirates and treasure hunts may be common.
Frozen expanses dominate the world. Perhaps great and cold mountain ranges are present, or perhaps frozen seas are common. Fierce arctic storms may be a regular occurrence. What is hidden beneath the ice and snow?
Great canyons, large mesas, and scattered arroyos are everywhere. Water may be in short supply or may be contained within massive rivers and reservoirs. These are often used as the backdrop for western worlds.
Vast expanses of sand are everywhere, perhaps with scattered mountains or rocky regions. Life clings (and perhaps thrives) at areas with access to water (seas, rivers, and oases). Trade and trade routes are a familiar element to these worlds.
Some magical force or unusual gravitational property keep these worlds functioning as a flat surface on which their inhabitants live. Watch out for the edges.
A cataclysmic event is currently ongoing, destroying the world as it is. Perhaps the world is collapsing into a blackhole, or perhaps a poison is slowly spreading across the land forcing inhabitants to don gasmasks and search for shelter.
These worlds resemble are own in their general climate and geological make-up. The landmasses may be different, and the inhabitants may be strange.
Ecumenopolis (City) Worlds
These worlds are dominated by a single, vast city that covers their entire surface (and perhaps beneath their surface as well). There may be specific regions for the wealthy, and other regions for the less fortunate.
Floating Rock Worlds
Great chunks of rock hang suspended by either magic or some unusual property of the earth. Travel to and from these locations may be difficult. Beware changes in gravity and sudden shifts in the rock tides.
Great trees of vast size grow here. Creatures and people may live in treehouses joined by bridges throughout the canopy or make dens in hollow logs.
Mushroom Forest Worlds
Grass seas are nearly endless. Depending on the length of the grass, this could be ideal for farming, grazing animals, or could tower over the head of the average person to create a canopy. These worlds are similar to savannah worlds, but generally have more rainfall and less trees.
These worlds are dense with varied and colorful plants and animals. There is beauty and danger here. Poisons, diseases, and predators may be around any corner, but so may be wonders beyond imagination.
These worlds are littered with debris. People may eke out an existence as scavengers. Perhaps these worlds are the remnants of old battles, the scrapyard for the galaxy, or just the realm where all discarded things end up.
These worlds are actually great beasts. They may be peaceful wanderers upon which people have built their homes, or they may be cosmic horrors that are struggling to awaken.
These worlds are actually colossal constructed habitats. They may be vehicles, artificial intelligences, weapons, or anything else. They may be obvious from first sight, or perhaps their nature is hidden under a coating of earth.
High mountains are everywhere. Like aerial worlds, transportation may rely on flying creatures or contraptions. Valleys between the peaks may be home to farmlands, or may be shrouded in mists that hold danger.
The entire world (or most of it) is covered in water. The people here may live on floating islands or aboard ships. What real land exists is scarce. Fresh water and food may be in short supply. Storms and great sea creatures may pose dangers.
Fresh Water Worlds
Great ruins from some long ago civilization are scattered across the landscape. Some of these ruins may still serve a function and be active while others may have fallen apart long ago and their purpose forgotten.
These worlds are wracked by savage storms. These may be blizzards, thunderstorms, massive dust storms, hurricanes, or any other type of dangerous weather.
A world that is entirely or mostly aquatic. The people or creatures here have figured out how to live underwater (either because they always have, or by constructing habitats or vehicles that allow them to do so). These worlds may be combined with oceanic worlds to create a dichotomy between surface and underwater or the surface may be uninhabitable (due to fierce storms or some other reason). Underwater leviathans may exist.
Fresh Water Worlds
These worlds contain massive underground cave networks or man-made tunnels. Like with suboceanic worlds, the surface may be uninhabitable for some reason. Food and light may be scarce, or people may have found creative or alternative ways to produce them.
These worlds are dominated by swamps, bogs, marshes, and other wetlands. Grasses, tall trees, vines, and water are everywhere. Beware of sinkholes and travel by flat bottom boats.
Tidally Locked Worlds
Tidal locking occurs when the orbital period of a celestial body perfectly matches its rotational period. This means that one side of the planet or moon will ALWAYS face towards whatever it is orbiting. This can result in the two sides of the planet (or other body) having extreme temperature differences as well as one side being perpetually lit while one is in perpetual darkness.
These worlds have massive geological activity and are places of volcanos, lava, and heat. Watch where you step and bring thermal protection.