Do you have a person that you want to focus your bio on???
You could look at how that person has contributed to the religion, or mabye how being invovled in this religion has affected their life...
I was toying with the idea of doing Hitler and his religous reasoning behind what he did (i am a history person) but then my school wern't to crash hot on the idea - so i didn't do that - i'm doing terribly boring religon and architecture.
Make sure you link the person to the religion clearly - and bring in as much source info as possible (history side again) so it shows that you know what your on about. I think the most importnat thing with a bio is that you don't just retell their life cause then its really boring - have something controversial or interesting![/COLOR]