Wallpapers are viewable on both Kubotsuki's and Totsutsuki's PCs. Both characters share the same set. There are currently 53 wallpapers to unlock plus a custom slot to insert the player's own wallpaper. Below is a gallery of all of them and their unlocking conditions.
Wallpapers
#0 Custom wallpaper slot - Instructions for replacing this wallpaper are written on it.
#1 "Factory Default" by FD - Default wallpaper for both characters.
#2 "Design K" By ZLD - Available from the start.
#3 "Design T" by ZLD - Available from the start.
#4 "A Trip to Metal World" by 001247 - Interact with the large fleshy trees in Metal Mounds until the panorama changes for a second.
#5 "Bad Joke" by gummy - Enter the innermost room in Clownpieces.
#6 "Mysterious Mime" by gummy - Find and interact with both Mimes in the Metal Mounds.
#7 "Breeze" by Jojogape - Find and obtain Totsutsuki's Cape effect.
#8 "Angel" by EBroxas72 - Enter the Angel Room in Purple Town.
#9 "My dreams so far..." by peppe_ykoba - Find and obtain the following Totsutsuki effects: Sunflower, Star, Music Box, Cape, UV Light, and Nightcap.
#10 "See, it's a crane!!" by gummy - Obtain the Origami effect and use its Shift action.
#11 "...Someday I'll learn" by EBroxas72 - Visit the Peeper Room in Winter Village.
#12 "Dreaming Parallel" by gummy - Play Uneven Dream for 30 minutes (not counting time the menu is open).
#13 "Chased" by EBroxas72 - Get caught by a chaser as both characters at least once.
#14 "Winter Dawn" by EBroxas72 - Sit on what's depicted in the wallpaper in the Winter Village.
#15 "The Showroom" by sniperbob - Enter the Sandy Showroom for the first time.
#16 "Handicraft" by CrystalCreation - Obtain 5 effects for each character.
#17 "Pyrotechnican Dreamers" by EBroxas72 - See both the Turtle Hole and Origami Flight events.
#18 "Spotlight" by 001247 - Obtain the Sunflower effect.
#19 "Graph Fight" by 001247 - Obtain the Pencil effect.
#20 "A worm?!" by Rurima - See the Appleworm's Birth event.
#21 "Blue Lovers" by gummy - See the Blue Lovers at Bumblebee Lounge.
#22 "On Deck" by gummy - Visit the Playing Card Maze.
#23 "Tickled Pink" by gummy - Visit the Pink Desert.
#24 "Radio Tower Outlook" by CrystalCreation - Visit the radio tower outlook in Rainy Garden (ver0.07 and earlier)./Obtain the Lily of the Valley effect (ver0.08).
#25 "Prayer" by EBroxas72 - See the Praying event in the Ice Chapel.
#26 "Terror Terror Bozu" by gummy - Visit the industrial path connecting from Stone Wasteland to Isometric Street.
#27 "PR0C355_F41L3D" by Rurima - Interact with the arcade machine in Concrete Treehouse that depicts a girl whose face is blacked out.
#28 "One Night, Cold Springs" by eltd - Visit the tubes in the Light Spa.
#29 "Make Your Mark" by eltd - Obtain 10 effects for each character.
#30 "The Nothing Store" by eltd - Visit the store (Geschäft) in Starlit Road.
#31 "I like the colors here" by EBroxas72 - Sit on the bench in Neon Park.
#32 "Below the Sunset" by EBroxas72 - Visit the pier in Windmill Lake.
#33 "Dormir Demais" by Rurima - Reach the main area of the Subconscious Garden.
#34 "Kubo Drift" by maple - See the 78 Skidoo event in Cube Road.
#35 "At the Top of the World" by 001247 - Reach the top of Forsaken Cliff's tower.
#37 "Incoming Traffic" by knuxify - Find the toys in Fast Food World.
#38 "Cosmic Rest" by rollaby - Have the Nightcap effect in inventory and visit the main area of Star Field.
#39 "BUY ME" by Moucky233 - Buy at least one item from either shop in Neon Village.
#40 "Kubo on the Mall Roof" by SkipFlow - Reach the roof in Abandoned Shopping Mall.
#41 "The Seer's Vision" by rollaby - Obtain the Seer effect.
#42 "Feeling Better?" by AcceleratingWind - Visit the Deranged Faces Zone.
#43 "Breezy Feelings of Greyness" by AcceleratingWind - Visit the Grayscale Gardenscape.
#44 "Positive Cuteness Never Expires" by AcceleratingWind - Visit the PC98 World.
#45 "Cinematic Cynicism" by AcceleratingWind - Obtain the Fast Forward effect.
#46 "Head of Nightmares" by gr33n - See the Hanged Kubotsuki event in the Playing Card Maze.
#47 "Draw Me Like One of Your French Seals~~~!" by EBroxas72 - Interact with the seal on the couch in either Sea or Water Palace.
#48 "Nail Board on My Head" by GwenDaArtist - Visit the Nail Board.
#49 "Doodles, Doodles Everywhere" by GwenDaArtist - Visit the Doodle World.
#50 "Ode to the Optimist" by GwenDaArtist - See the Goodbye Totsu event at the Heaven's Docks.
#51 "End of a Sweet Dream" by GwenDaArtist - See the Trixboa event in Galleta World.
#52 "It's cold in here" by River - Obtain the Hoodie effect.
#53 "Blinded" by rollaby - Interact with the TV that displays the blindfolded woman in Corroded Dream.
Bonus Wallpapers
Bonus wallpapers are wallpapers that are present in the [Bonus Wallpapers] folder of the game, but are not available in game, either due to being too close to an existing wallpaper, or due to lacking a proper trigger to implement them. They can still be used by using the custom wallpaper feature and replacing the default wallpaper by one of those.
Bonus Wallpaper #1 by gummy
Bonus Wallpaper #2 by sniperbob
Bonus Wallpaper #3 by ZLD1
Bonus Wallpaper #4 by minty
Removed or Modified Wallpapers
Old version of #14 "Winter Dawn" by EBroxas72 - Was used until ver0.08.
YNOproject Wallpaper
Due to YNOproject not supporting the custom wallpaper feature, a defined wallpaper has been set to it instead since the release of the Ver0.08. It can be used offline too by setting it through the custom wallpaper feature.
Picture taken during the Ver0.08 tour replacing the custom wallpaper on YNOproject.
