What could i compose a fanfare about?

Im taking GCSE Music and I need as much pratising as I can on composing, i`m quite okay at it but I was thinking of following the footsteps of Mozart, Beethoven or Tchaikovsky (as they inspire me when it comes to writing music) and I was just thinking of a really good suject to write a fanfare about, something really different and unique and pehaps any ideas on a key signature to start me off?