We planned this feature at some point. But i guess at the end there was no time for that anymore. Sorry.
Thanks for the note, I am really loving this game so far--which is precisely why I'd love to be able to fuss with things like custom portraits.
I would love to see it any future game like BD (if there is one.) On the other hand, when there is full modeling on an onscreen face as in NWN, Morrowind, and KotoR, portaits are just distracting.