<p>The less well-known the less likely it will be a cliche.
Remember the essay question is meant to reveal you, not the historical person, so write it with that in mind.
So, if you pick Cleopatra, the first thing that will pop into most readers minds before reading the whole essay is that you are attracted to glamour/power. If you pick Catherine of Aragon the reader will assume you are an Anglophile, or a fan of The Tudors on showtime. Stuff like that.
It’s a fun topic to play with, so brainstorm before you decide.</p>