My first reward was a book at 5%.
Then for my second reward which was reaching 299 -and- sticking to program for 3 months, I splurged a little on new clothes. (2 pairs of pants, 3 tops, a belt) Ones that will last me a good 50 pounds or more.
My plans are to continue to reward myself with books or little items for every 5%, but then every set of 3 months to "splurge" on a new piece of clothing or something bigger.
Weight based rewards and time-based rewards for how long I can stick on plan