Hi, yes I'm familiar with the comics.
The first three are indeed Doug Tennapel's work, found on the archived Neverhood website.
The last one looks authentic, might be from his Sketchbook Archives, but I'm not sure.
Old Neverhood site with zip files of the official comics
Doug Tennapel Sketchbook Archives vol.1&2
I occasionally replay "The Neverhood." My dad and uncle used to play it and I watched them one time when I was really young, I didn't understand half the puzzles. But I thought (and still think) the music was hilarious, the dumb jokes and style of the game was interesting, and the story is unique.