Well, this isn't an official design document, but here are the answers to most of your questions:
but what kind of game is it?
It is a first / third person action / horror game. Something along the lines of Manhunt for PS2 or Thief for the PC.
where does it take place? earth, space, or other? what time? 1920's, 2006, or 3040?
It takes place on earth this century.
are they humans, monsters, aliens, What?
What are they doing? puzzles, killing, racing what?
Mainly killing with guns and butcher knives, maybe chainsaws or other objects
Is it for kids, teens,, Adult?
Mature rating 17+
need more info to start making comps for maps, backgrounds, characters, costumes, weapons?
Also what is the story, plot, conflict, Problem that the players will solve?
also basic color pallet would also help.
Each story is based on the character you choose. One character (which I will use for the demo) will basically be based on Jason from Friday the 13th (no mask). There will be like a cut scene in the woods at night near a cabin on the lake. Some young adults will be sitting around a camp fire telling scary stories. The scene is based on you watching it. Eventually, one of the girls gets up and states that she is going to go take a shower and go to bed.
After the cut scene, the game starts with you standing there holding a butcher knife. You are free to roam whereever you like (like GTA: Vice City). If you want you can walk over to the cabin and watch the girl take a shower, you can kill whenever you want. The overall goal is to kill all of them before they call the cops.
I haven't thought of a point system or how to actually make it tough yet.
Another character will be a sniper which picks his spots to be unnoticed and just picks off anyone and everyone. More points for headshots, etc. This will be more of a city scene.
Another character will be a disgruntled worker. This is an office scene where you have to pick off as many people as you can before you get picked off by the SWAT team (kind of a time limit scenario).
The name of my gaming company is Nocturnal Games (http://www.nocturnalgames.com) and the name of the game will be Twisted Souls
For the Jason character, the color pallet could be like the placeholder on the Nocturnal Games site.
and what artist do you like in games?
I really liked Keith Parkinson's art (EverQuest). I also like Dmitri Savinoff (http://www.savinoff.com) and Digital Blaphemy (http://www.digitalblasphemy.com)
yeah lots of questions but the more I know the better the design. :)
Does this sound like a cool game? I have a lot of writing to do ...