I'm not sure exactly what the problem is. What are you comparing with in contrast? Some portraits are pre-made, not actually generated in the photobooth level, like the origin portraits for example. Multiple NPCs too. Once you use the mirror, it generates a new portrait every time, in case you've made any visual changes, that's why the portrait changes then. This is also why some people complain their portrait being "uglier" after using the mirror.
So if you'd like to change that, you'd have to mod the photobooth level and adjust the cameras for every race/gender respectively to your liking.
