Triptych: Katamari Zeldacy

"Link" by Andrew Wilson

"The Legend of Damacy" by Leo Wiggins

"It's Dangerous To Go Alone!" (t-shirt) by Samantha Smith

Triptych: Finn Is Made Of Rockets

"Adventure Time Art Deco" by Aaron Wood

"Super Finn Bros." (t-shirt) by Dean Lord

"Katamari Time" (t-shirt) by MeleeNinja

Triptych: The Wonderful Land of Ooo

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"Adventure Kong" (t-shirt) by BazNet

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"Choose Your Own Adventure Time" by Das Chupa

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"Adventure Time: Land of Ooo Katamari" by Marcos Henríquez

Triptych: Katamari Fever

"The Prince With A Fez" by MeleeNinja

"Aperture Damacy" by MuriraRK

"Katamari Portal 2" by Squid Von Bob

Triptych: Play All The Games!

"Indies Assemble" by Steve Courtney

"Captain Valve: The Animated Series" by ZeroLives

"Katamari" by Jeremy Tinder

Double Triptych: We Do What We Must Because We Can

"Queen of Portals" by Sodano

"Portal Minimalist Poster" by Blind-Pixel777

"Aperture Dalek" by The Dalek Factor

"Katamari Portalcy" by Brittany Langlois

"Portal 2: Minimalist Poster #4" by LMND Tree

"Cutaway Companion Cube", Artist Unknown

I'm not sure where that cutaway Companion Cube came from, or who made it. It might be official Valve artwork promoting the new Portal 2 DLC, "Perpetual Testing Initiative". Then again, it might not be. Your guess is as good as mine.

Triptych: Katamari On The Rocks

"Pimp of the Cosmos" by Devon Cady-Lee

"Katamari" by Michael DeForge

"Katamari Dance Party" by Matthew James Taylor

Triptych: King Of The Cosmos Am Disappoint

"The Little Prince" by Fort Awesome Studios

"We Love Katamari" by PronouncedYou

"Katamari Damacy Jelly Beans", Artist Unknown (possibly official game art?)

Triptych: Spelunking Anecdote

"A Story About Caves" by scrotumnose

"Doukutsu Damacy" by Alex Ahad

"Cave Story" by 8-bitch

Triptych: You're A Lonely Rolling Star

"Katamari" by kozyndan

"Katamari of the Dead" by Hector Mansilla

"AXOR Heroes: Katamari" (print) by Axel Pfaender