There is a Wolfenstein 3D room for ghost hideout, a DOOM level for Gearhead Vault, the Quake title screen in the Wasted Garage. Look it all up on youtube for proof.

There's also an 'id room' in the distillery, but I haven't found it yet.

Also saw some photos of Tim Willits and Todd Hollenshead (id Software guys) on a desk in the Dead City.

Re. the Quake buttons in Wasted garage... there are four. I've only found one.

An ammo type to the minigun called BFG if a refrence to the BFG in the DOOM seris.

this is....AWESOME

Various DOOM 2 Cups
Quayola Quyaons - "64 shades of brown!"
Wolfenstein room
Doom room
Quake room
Blake griffin bobblehead (remember the ad for Rage - Get blake Griffin in RAGE)
Doom guy bobblehead
Quake plushie
Vault boy bobblehead

Anyone notice Maledict's face in Dead City? Appears twice, on the walls.

Maledict is from Doom3.

• Quayola Quyaons, obvious reference to the different shades of brown in Quake!
  
• On Mayor Redstone's desk, the Blake Bobble Head is NBA Player Blake Griffin.
  
• On Clayton's desk, the mug has the Doom logo.
  
• The Wasteds' Garage has a street sign that reads "4 8 15 16 23 42", a reference to Lost, the numbers that Hurley had to win the lottery.
  
• I ran into an Authority guard standing next to a can, told me to pick it up. When I did, he called me a," Good boy." Half-Life 2, anyone?
  
• Found a poster in the Dead City Center, read " 50% off on Rage 2, Doom 5"

Inside the Wellspring Bar, the book that the guy is always reading is the http://www.doomworld.com/10years/doomcomic/comic.php?page=0.

Flip through the pages and you'll find the ones he's reading... I was to lazy to run the game to find the pages

Carmock (I think that's how it's spelled) Plaza. On the office building's directory.