In an email from JeffStoat, the identity of the last Cylon model is revealed:

I think I've worked it out. The Final Cylon is...

Doc Cottle.

He's the only major character missing from the
Last Supper picture, and he says 'Christ' in an
episode of Season 3 - there is no Jesus in the
polytheistic religions of the Colonies. D'anna's
'forgive me' comment in Rapture might be in
relation to Cottle's actions regarding Hera,
the Cylon-Human baby. Pretending it was dead,
and so on. D'anna was especially worked up
about the little brat.

Also from a recent email:
Me: I wonder what [Roger] Corman could make with $200 million.
Jeff: easy. 20,000 movies.