From Top Left to Right each row

-Death (Have a Nice Death) , Death (Discworld) , Kel Thuzad , Duskull, Doot Skull, Skull Knight, Death (Good Omens), Lich (Loop Hero)

-Skul (The Hero Slayer), Lord Hater, Inferno Cop, Papyrus, Sans, Ghost Rider, Ainz Ooal Gown

-Smitty Werbenjagermanjensen, Manny, Mr. Bones, Jack Skellington, Brooke, Death (Castlevania)

-Spinal, Honda-San, Dry Bones, Grim (Billy & Mandy) , Death (Soul Eater), Bonejangles, Gravelord Nito

-Sir Daniel, Dry Bowser, Summoned Skull, Skeletor (honorary skeleton, mostly just a person)

Source: https://www.newgrounds.com/art/view/burdrehnar/welcome-to-the-bone-zone

Untitled

Welcome to the BONE ZONE!!

Source: https://twitter.com/Burdrehnar/status/1544778736503033857?t=hz2GZ74xWVT5xCsrQvCYXw&s=19