Inside Dungeon:
Grand Forest: Floors 1-5. A thriving majestic forest. Home to forest like creatures and a few demi humans. Example: horned rabbis, 3 horned stallions, goblins, Dire BeastWolves, and Hind Bears etc. Boss is the Red HindBear a variant of Hindbear that is twice the size and is stronger and faster than a normal one and is capable of breathing fire.       
Labyrinths: Floors 6-11 A long maze like labyrinth.Mostly home to half beasts. Example: minotaurs, orcs, ect. Boss is the Minotaur Executioner a giant Minotaur that wears rusted armor and wields a giant hammer axe.
Swamplands: Floor 12-17 A large murky swampland. Home to insect, fish and reptile creatures. Example: lizardmen, grand catfish, giant mosquito etc. Boss is DakaGator a six legged alligator that is capable of using water magic. 
Desert Ruins: Floors 18-23 An ancient forgotten ruined that is home to many species of undead and desert creatures. Examples: Rotting Mummy, Desert Lizard man, Living Hieroglyphs. Boss is Desert Pharaoh Setamun an undead mummy king capable of casting power curses and magic.   
Victorian Ghost Town: Floors 24-29 A old abandoned Victorian England city that houses many of the forgotten and undead. Example: War shadows, ghouls, the restless(evil spirits), Igors, is Boss Franky the Butcher a Frankenstein like monster standing at 20 feet tall that kills with his clawed werewolf right hand and a rusted cleaver in the left. Mostly uses buff spells. 
Frostlands: Floors 30-35 A frozen tundra and arctic like landscape where mostly arctic creatures or Frost Giants are capable of residing. Example: Polar Hindbear, King Orca's, Giant Leopard Seals, Frost Giants. No current boss for this area.
Treasure Trove: A cavern like landscape filled with treasure. Home to mostly lesser dragons, or dragon like creatures. Example: Wyvern, Dragonnewt, Drake. Boss is Cavlog the Draon of Greed. A dragon with scales of multicolors like the jewels inb its cavern. It's fire is capable of melting platinum and gold.
(Btw the creatures used in the listing of floors are only example of what could be found in each floor. If you have a creature taht fits the setting use it. Even if it isn't real or not.)
(Will be updated if you have any idea's for more floors or outside dungeon locations please let me know)