The ranks for the worlds are up for discussion, but here are some ideas: Giant World- looks like a normal singleplayer world would be, except everything is huge. Planetoids/Landblocks- Planetoids (for examples, simply search "planetoids" in google images) or flat "clouds" of land, each made of a different material, all floating at various heights. Rainbow Park- Large flat land with some hills- various parts of the ground are different colored "splotches" Monster Caverns*- Obsidian sky with lava pillars/lakes with plenty of stone caves and mushroom patches. *Would this be too much like the Nether? Sorry for the large post! ^^;
Thank you for the consideration ^-^