There are 5 new costume keys available right now for Dead Rising. below is a list, and how to access them:

Marketplace:
Cold Hearted Snake

In Store Kiosk:
Accountant
Burgandy Wine (larger file size than the MP version?)
Pure White Suit
Stripe

The keys from the Spetember kiosk disk DO NOT WORK as of yet, and Capcom has not responded my queries. The Snake one is available on Live as we speak, and is a neat snake skinned suit.

I'll have more info on the kiosk keys and why they don't work at a later date.

UPDATE: I can confirm that the Dead Rising Kiosk Keys are ONLY available at EBGames/GameStop kiosks. Wal-Mart and other retailers will have a kiosk disk sans content!