Edit: Figure out what nine of these are and I'll give you a cookie. Some of them are original creations. Many of them are from the same settings.
Many of them are vague, but I suspect that was the intent.
Well, time to give it a try!
[] A world of bloody evolution.
RWBY
[] A world once enlightened, now slowly seeping with poison.
Phaaze
[] A world of sunny days now clouded with darkness.
Kingdom Hearts
[] A world of magic and science, now a broken ruin.
A Certain Magical Index/A Certain Scientific Railgun
[] A world of depths and hidden places, where nobody has ever seen the sky.
Bioshock
[] A world of violence and conflict, stalked by a broken-hearted god.
Worm
[] An infinity of worlds, where men fight each other - and worse - in the shadows.
Dominaria
[] A world of madness and change, where only the violent and prolific thrive.
Warhammer 40K
[] A world where men and bugs fight for supremacy, while ancient glories still stare down from the sky.
Starcraft
[] A world built on the promise of progress - and it's shadow.
World of Darkness
[] A world of death and ambition.
Phyrexia
[] A world of broken pieces, where life yet prospers.
Alara
[] A world of struggle, where men crushed beneath the earth reach for the sky.
Mirrodin
[] A world of metal with rot in it's heart.
New Phyrexia
[] A world of gleaming ruins and steaming jungles, studded with the lost wonders of bygone age.
Zendikar
[] A world where dwarves dig for treasure and hammer out masterpieces, their eyes glinting of madness.
Dwarf Fortress
[] A world that laughs at the limitations of size, where men scurry like ants and ants crush men beneath their feet.
Exalted
No idea what these are:
[] A world of great beasts and those who worship them.
[] A world of order and law, and those who would enforce them.
[] A world of violence and freedom.
[] A world of magic - and witches.
@Angle , will we get QM confirmation for settings?
Also, my vote:
[X] A world of madness and change, where only the violent and prolific thrive.