For those wondering, what to do to get wallpaper #97 (like me), here's what the code says:
1. Chainsaw a Monmonzu.
2. Touch the piano.
3. Take any of the passages that lead to the river in the Tribe Settlement.
4. Enter the TV gallery (it doesn't require you to interact with anything)
5. Watch the dancing pyramids event.
6. Chainsaw the blood-drooling creature from the Underwater Amusement Park (there's 2 more events associated with this switch, but I can't locate them on the map, so I'll settle with this one)
7. Visit Farm World A.
8. Visit Farm World B.
9. Find the submarine.
10. Visit the UFO in the Head Wasteland.
Each one of those actions triggers a switch, and once all 10 switches are on, you will get the wallpaper once you wake up and go to your PC. Supposedly.