You could talk about something you have done but you don't want to do it again (try to choose a funny, embarrasing or scary thing ^^ nothing really serious...) explain the situation and your reasons, even if you think they are dumb. A little story is always interesting and you will be talking about you ! ... and you know you perfectly ! Maybe they will ask you silly questions to know a little bit more ( to basically mock you, classmates are 'mean' ... =p ) about the event and everybody will laugh but you'll have a great time ! ^^

Talk about your family!

Best thing to talk about it is something happenned to you and you want to share that event with others. Because if tell a story you will grasp the audiences' attention. And believe me, all people like stories. I hope you do well and be the best speaker.

You could tell the other students about Italki.

amena,so many things you can talk ...like me.. haha