By the looks of it, if you are a Penguin of the Week you will now be receiving a special background in addition to 10,000 coins and the Green Viking Helmet. When Club Penguin updated last night they added a new Penguin of the Week background to their files. It looks like this:
It is unknown if former Penguins of the Week will receive this background but it would be likely they do, as otherwise it would not be fair.
Thanks to Saraapril for the tip.