Floor 188 is a giant dry erase board, and the only markers available is one rainbow one that switches between colors every hour. Anything someone draws on the board will come into existence, as long as it can't destroy the floor or building. The only way to get into is is pick up the marker, which teleports randomly between all the floor every time it changes colors.

Floor 189 is exactly like floor 188, but it is 200 feet above floor 188.

Floor 190 is discontinuedly flat, with some holes on the ground, which can let you go down to the beneathed floor.

Floor 191 is only accssable by the other elevator.

Floor 192 is the plane of fire

Floor 193 is an invisible hotel.

Floor 194 is a board to remind everyone that they need to make a way to have the floor they make be accessible, no matter how complex or simple. You get to this floor by forgetting a rule.

Floor 195's button on the elevator is broken.

Floor 196 is a huge room with doorway teleporters to every room that has existed and will exist. The way you get here is by saying you are lost.

Floor 197 is Frostfell(you've got to know a lot of D&D lore to know what frostfell is)

I think you should leave a D&D lorebook on floor 197.

Floor 198 is a floor you are teleported to whenever you forget to comment on the floor before your's. There is a single computer there with internet access. The only way out is to edit your post to make it comment on the floor before yours.

floor 199 does not exist. if you got to floor 199, you go to a random floor.

But what if the random floor you get is 199?

You reach floor 200 once you've visited at least 200 floors using each elevator. You are allowed to repeat floors. Floor 200 itself is a massive ballroom, with the word "Hello," written across every surface in golden ink. By saying hello back to each writing of the word, the color of the text changes to a random color, and a spectral figure appears In front of you. Each figure has a unique personality and will strike up a unique conversation. After which, the figure will proceed to dance on the ballroom floor. Once every hello has been conversed with, a ghostly tune emerges from nowhere, and the figures invite you to dance as well. 

If you press the elevator button for floor 201, you go to floor 202.

Floor 202 is the astral plane.

If you press the button for floor 202, you go to floor 201.

Floor 201 is an enormous beehive. Just steer clear of the giant bees and you should be fine.

Floor 203 is a normal office building floor, and all of the inhabitants are oblivious to the rest of the floors and the weirdness that goes on in them, and they refuse to believe that such floors exist, even when they are taken to those floors. You get here by normally pressing the elevator button for this floor.

Floor 204 is a mash-up of all the previous floors, and all the future ones too. Plus there's a portal to floor 298.

You reach floor 205 by standing in the middle of Floor 1's lobby for 205 minutes. After exactly 205 minutes pass, you fall asleep from boredom, and wake up at floor 205.

Floor 205 is a burning waste of red rock, littered with bones and pools of magma. The only way to leave this floor is to kill some of the beasts that live here, craft a comfortable bed with their long, rope-like hair, and sleep. When you do so, you are engulfed in a ball of flames, and appear in Floor 1's lobby screaming and charred.

Floor 206 does not exist. Seriously, don't look for it.