I don't think you should even think about your final piece yet. The idea is to explore whichever theme you choose and then naturally come towards a decision for what you want to do for a final outcome. I found that when I let the process just happen, I produced much better final pieces, but for my exam unit, I put too much thought into it and didn't produce a very good piece, and I lost a few marks.
As for a theme, I like the idea of fragments, but whatever you choose, you can always manipulate it and make your artwork about something you find interesting, as long as there is a tiny hint of the original topic left in there.
Dont forget to enjoy yourself, as art is supposed to be enjoyable, but I found that a lot of people let it get them stressed out and they didn't do so well!