I had planned on giving myself weight-based goals, but those sort of fell through. Recently I changed my mind and decided to do time based ones instead, although not on a weekly basis but after completing big goals.
For example, after I finish the 30 Day Shred, I'm going to buy myself a new pair of tennis shoes (which I really need anyway, because when I went to buy them at the beginning the guy convinced me to buy 8.5s. For the record, I wear a 6, and I've tried wearing them so they are unreturnable )

. After that I am either going to repeat the 30 Day Shred with heavier weights or move to a different program. I haven't decided on what that reward will be, but I am excited to!