Yeah, to add a new portrait you basically have to:
* Add a new icon to portraits.dds & resave the file
* Add a new IconUV item to Main\GUI\portraits.lsx
* Add a new MaleIcons or FemaleIcons item to Mods\Main\CharacterCreation\properties.lsx

To change the portrait in an existing save change the appropriate Characters -> PlayerData -> PlayerCustomData -> Icon property for the character.