I tried writing a bit of one, using the Dido and Gandhi pages for inspiration – it's a bit short (I added a bit since posting it in IRC) but I wasn't sure what other filler to add, and it seems to forget the 'Cullen' part of her name but oh well.
Welcome, Empress Regnant Isabella, bringer of change. Your daughter, so swiftly taken from you, broke free from the shackles imposed upon her and called on you for aid. You rebuilt the hidden world, defeated those who dared trespass against you and yours, and started the steady march out of the shadows.
Swan, a name shared with the creature of such majesty – do you have what it takes to succeed, reach out of the depths and reveal yourselves to the public? Can you build a civilization that will stand the test of time?
Examples can be found at the end of each leader's page on the Wikia for Civ5 (list of leaders), under "Intro". (Example.)
If you have particular inspiration, why not write one for a character (a favorite or one of your own)?