Every year they give out a gift for gold and platinum members. It's different each year. Last year for intance it was something like a set of three posters for Kid Icarus Uprising, Skyward Sword, and Lugi's Mansion. There is a Gold Reward and a Platinum Reward. If you're a Platinum Member you can choose between either one.
I had completely forgot I signed up for the Skyward Sword reward for Platinum status and never received it.