Bring back old giftcard options and add new ones. Offer Riot RP Cards!
If you want some serious increase in Bing usage and people using the rewards program offer Riot RP (Riot Points) cards for League of legends. It is the most popular game in the world, and I know I referred 100's of people back when there were referrals. Many players are young and don't have a credit card or a car to go to the store, and this allowed them to buy game credits online. People would get points to buy subway gift cards which could be used in the League of Legends store in exchange for Riot Points.
That being said, could you please bring back the subway gift cards? I'd also like to see a CVS/Walgreens gift card. Hope you listen to your users and make this available once again.