I have a couple of pieces of advice for you.
If you have more than one student speaker come up with a list of topics among you and assign them. In the course of planning our pinning ceremony I attended the ceremonies of several other classes and I found that most of the speakers went over the same topics. They all talked about how much their families had to put up with, how much they were going to miss their classmates and that one time in clinical when.....
We wanted to avoid this, and to make sure that the speeches that were given reflected the diversity of our class, so we had one person talk about the experience of nursing school
and the challenges that we and our families faced, another person spoke of the bonds and friendships that developed among the students as a group and how we were unique, someone else spoke from the male/returning student perspective and we had someone speak about the faculty and their influence upon us. It went beautifully, and with a set topic in mind it was easier to reminisce and organize the material.
As another poster stated, please use stories to bring the people who are attending your ceremony into the world that you have shared with your classmates. Good luck and let us know how it goes!