Nergle was super fun to design as he's just a buffet of everything thats kinda gross. As he's a avatar of death and life I wanted him to feel like he is both rotting flesh and growing plant life.
Slaanesh was tricky to design, but after settling on a super smooth almost rubbery texture for him that at first glance is alluring but on closer inspection would feel horrible.
Tzeech is usually associated with birds and aquatic life, i also liked the idea of the image of him as a hunched robed wizard is just a shroud over twisting tentacle madness.
Khorne is the embodiment of Warhammer's heavy metal influences. He's the oldest of the chaos gods so i thought it would be cool to have him be made of jagged rock with a hateful molten core.