Flowers are always nice.
Especially if you have pansies! I always like having a tall, medium and smaller vase of flowers all paired together with a mirror under them. It looks really put together. Should check if there is a "flower limit" with panhellenic first. That was the one fine we got from office as we were over one flower arrangment. As for desert, we had cheesecake on a stick and it was a huge hit with the pnms.