This was copied from wiki V.1 on 18th July 2013. Most of the external links are now broken need to be revised. The early Bioware links are broken forever! It is a short, and not very informative set of notes on adding portraits to NWN.
One of the easiest ways to enhance the build is too add portraits to the ./portaits folder. NWN requires 5 of a given size in.tga format. Bioware have published a “How to make custom portraits guide!”
Bioware have a page about adding Custom Content. Portraits can be added to the ../portrait folder, but will be offered as possible portraits irrespective of the gender of the protagonist. The portrait.2da hack is probably required to make the character builder aware of the gender of the portrait. The file naming convention mandates a gender flag.
The hints above may be findable using Goggle.