I found this to be a huge problem with D:OS2's character customization and was hoping it wouldn't be the case with BG3 what with the new face scanning tech. Sadly, aside from the default heads, all of the face options appear be European/Mediterranean looking of ages ranging in the 30s-40s. Humans in the Forgotten Realms have always been portrayed as the most visually diverse race with influences from a multitude of real world cultures and I find that this is just not adequately portrayed in the game.
From what I've read, the way Larian created all their head models was from scanning 40 different people and tweaking the models to create 150 unique faces. I understand that, being a Belgium-based company, it might be expensive to hire and fly out foreign models/actors to create more, especially during the current times. However, I was looking through the head options of the other races and found some pretty good ones that would be easy to tweak and add to the human pool for more ethnic variety.
West Asian Female[img]
https://imgur.com/a/wOGUDry[/img]
African Female[img]
https://imgur.com/a/vvms9N6[/img]
East Asian Male[img]
https://imgur.com/a/yGh9asp[/img]
Polynesian/Indigenous Male[img]
https://imgur.com/a/4nbqtwF[/img]
Hopefully, when the global pandemic dies down, Larian will consider scanning more people. However, it would be very simple for them to tweak these heads using their modelling tools and include them as human options in the near future.