The first picture is just a pun, second picture is a delirious design where he played as a spooky jack-o-latter guy. And the last two pictures are left 4 dead inspired, with mini being the witch, tyler as the tank. While Evan is the smoker and delirious is the hunter. Mini and Tyler have a “forget me not” flower, remembering each other while delirious and vanoss are just hanging out as infected boyfriends.
first picture: video around 8:07
second picture: video