Before I read the flower pot idea, I was thinking that too. The other day a student gave a fellow teacher a cute flower pot filled with foam. Then there were little "stakes" in it. On each stake was like a little chocolate bar or something. Then there were a few fake flowers. It was so cute. It was the mother's way of saying thanks for putting up with my son all year. (I should get 6 of them!!
Anyway, you could easily do the same thing. Rather than candy bars but on the gift cards.