We've got a few broad classes. Initially, we'll have four groups:
$1 rewards - I'll put together a crappy video, in a "scavenged" costume voted for by backers, and read off the list of $1 backer names while 'fighting' off 'zombies'.
Then there are:
In-game rewards - We'll introduce names into the random name generator, let you design an NPC with equipment and special we'll stick into the game, add a house floorplan based on your actual home, that sort of thing.
Digital Art Rewards - I've already got an artist working on commission work for the kickstarter. Basically, this will allow you access to high resolution art and digital wallpapers, and will be fairly limited to start with.
Extreme Supporter Rewards - A custom assembled completely unique Cataclysm themed "Survival Kit" (danger: do not rely on Survival Kit fo survival) for our most generous backers. There will only be a very limited number of these, and I'm hoping to price them high enough I don't have to make any.
Once we've met our goals, we'll add more reward tiers (and expand existing reward tiers) based on stretch goals. It's important that we only offer awards we can afford, after all, and our initial goal is quite low.
But eventually we'll be hoping to introduce a Physical Art tier to get Cataclysm posters, and if you back that tier you'll get an a poster for each of 3 stretch goals hit, in a variety of styles. We'll also expand the Digital Reward tier.
We've got more planned than that, and I'm leaving out most of the details (and all of that is subject to change in the next several weeks), but that's a rough idea of what we're aiming for.