Triptych: An Army of Mantis Men

"New Slaves Pt 2: Thank You, Yeezus" by Raphael Phillips

"GlaDOS" by Kat Rocha

"Mrs. Potato GlaDOS" by MeleeNinja

Showcase: Video Game Quotes by GamerPrint

These have been making the rounds for a while, so you may have seen them. I'd put any one of these up on my walls.

[GamerPrint: Video Game Quotes]

Showcase: Joey Spiotto's Little Video Game Books

"My and My Big Daddy"

"The Cake Is A Lie"

"The Littlest Dragonborn"

[Joey Spiotto on Blogspot]

Triptych: It's An Aperture Christmas

"Portal 2 Chell Pinup" by Andrew Wilson

"It's Been A Long Time" by spittfireart

"She Sees You When You're Sleeping" by SyntheticPH

Triptych: Lie-Cake

"The Cake Is A Lie" (t-shirt) by Adam Works

"Mommy's Little Fatty" by Kei-Chan

"Still Alive" by DoomZilla

I'm still not entirely sure how I came across that Portal\Adventure Time mashup by Kei-Chan, but man, a fat turret getting berated is always comedy gold.

Triptych: A Rip In Space-Time

"Portal 2 Minimalist Poster" by DirtyGreatPixelsUK

"Companion Cubism" by Dann Matthews

"Because I'm A Potato" by Blimp Cat Studio

Triptych: Aperture Science Posters

(click for full-size)
"Aperture Science Camp" (t-shirt) by The Hookshot

"Aperture Volunteer" (t-shirt) by DarkChoocoolat

(Click for full-size)
"Aperture Science 1953 Poster" by DJ Corny

Triptych: Wheatleys Gonna Wheat

"Portal: GlaDOS and Chell" by Bear and Robot

"W For Wheatley" by DoubleLeaf

"Science!" by Aaron Wood

Triptych: Katamari Fever

"The Prince With A Fez" by MeleeNinja

"Aperture Damacy" by MuriraRK

"Katamari Portal 2" by Squid Von Bob

Triptych: Portality

(Click for full-size)
"Portal 2: Abstract" by Bruno Pires Santos

"Thinking With Plungers" \ "Thinking With Plungers 8-Bit" by Adho1982

"Portal For NES" by Illustrography

Showcase: Kamil Khadeyev's Minimalist Valve Posters

[Kamil Khadayev's Tribute to VALVe Software]

Showcase: Combustible Lemon Launcher

(Click images for full-size)

(Aperture Science's Combustible Lemon Launcher: Contemporary Version, '80s Version, '60s Version)

Riffing off of a reference from Cave Johnson's vitriolic monologues in Portal 2, TheLoneRedSheep has mocked up a timeline, from the '60s to present day, for an Aperture Science Combustible Lemon Launcher. Because when life gives you lemons, the easiest way to burn down life's house with those lemons is with a lemon-launching device of some kind.

[TheLoneRedSheep's DeviantArt]

Triptych: The Woman With The Portal-Gun Arm

"Portal Poster" by Red Corner

"Have You Ever Seen A Portal?" (t-shirt) by Michael Mohlman

"Saul Bass-Style Portal Poster" by Starflier