Refresh the game in your browser and the new images should show up.
As for when you can start playing, the Advent Calendar begins on December 1st at 00:00 Pacific Standard Time and you will get your last daily Key refill on December 25th.
If you play every day and use your key each day then you will never need extra keys to complete the game. But if you miss a couple of days, say over a weekend, when you return you will only have the 1 free key to use. Therefore any keys you earn through friend requests or purchase will assist you when you have more available doors than you have keys.
Last edited: Nov 30, 2010