For my game, at first, I didn't feel good enough an artist to draw busts for all my characters so I've gone a mixed path: busts for important ones and classic facesets for the others.
Every tester reported this as inconsistency and they're right.
So I decided to grab my mouse firmly and start drawing my own art in addition to ressources I already had, so that I can make busts for everyone.
That's a tough job, especially when you can't draw, but I think busts will be more efficient than faces for my adventure game.
If the focus had been combats, busts may have been too much of a presence on screen.
But if your game is character-centered, you'd want to show them. After all, *they* are your story.
Next problem I had to solve was: should I make busts for everybody or only important characters?
I've chosen the hard path. Busts and names for all.
I know that players identify an important NPC when they get to see a faced and named one. So having all NPCs like that may be disturbing, but it's consistent with the vision I have for my main character.
For him, every one is an important living person. But I don't know the players reactions to it yet. Maybe it's a bad move, maybe not.
I should add that, independently of having faces or busts, make sure to have at least a handful different emotions to show.
I've seen games where a cheerful smiling girl basically said "the town is on fire, people are getting slaughtered!" and that just doesn't work at all.