I don't know anything about Quake3 (chiefly because I don't have it :P), but I feel compelled to help.

I KNOW! I can be one of those concept guys. I'll come up with a storyline, planets, and other stuff relating to the job.

PM me for any help. As i'm writing this, i've got some ideas simmering in my grok pot.

-ThO

Edit: Some planets for you:

Aquaticus

Climate: Sunny, some rain
Landscape: Mostly water
Description: Known for it's lovely beaches and wide expanse of water, Aquaticus is a tourist haven and a living area for sapient water lifeforms.

Sandicon

Climate: Arid
Landscape: Desert, occasional river
Description: Sandicon is a land of the ancient Scorpions, a race from long ago. They have built citadels, temples honoring their gods, and vast palaces containing riches beyond belief.

Starship Plaston

Climate: It's in space.
Landscape: A starship. Nuff' said.
Description: The Starship Plaston was named after the great rabbit thinker and writer. Help save the crew trapped on the ship.

Pluvius Frigda

Climate: blizzards, ice, sunny
Landscape: Icy, mountianous, some sea
Description: Pluvius Frigda is a frozen land. Be prepaired to go on the ice!

Giant Rubex Cube

Climate: Sunny, no rain
Landspace: Plastic
Description: This is not a planet so much as it is a huge puzzle built by engineers for laughs. A robotic machine is inside constantly moving the landspace.

-ThO