I just received Daria Mueller, "Guida agli affreschi astrologici del Salone di Padova" (2007), printed through Lulu -
http://www.lulu.com/content/1515488
It is nicely done little book which tries to account for all (I think, I haven't counted them) of the frescoes, and offers a theory for these details which seems to base it on Firmicus Maternus' "Mathesis Libri Octo" (sometimes written "matheseos").
An outline of her theory is given at her page -
http://www.dariamueller.com/articoli/saloneastrologico.html
The bad news is that she does not provide pictures of every fresco, and those that are there are small. Among those not provided is ours.
The good news is that she describes ours:
"Vescovo seduto, onorato da due dame". A seated bishop, honored by two ladies.
She considers that this, along with the one above it, represent people born in the second decan of the sign of Aries, ruled by the Sun. This means people who rise to the heights of nobility and power.
So... it still looks like a FEMALE bishop to me, and I think it should be unusual to have two ladies waiting on a bishop. But, the facial features on even conversus' image are not distinct enough to make me bet the farm on it being a woman.
Ross