Suppose that the predicate "human mind cannot create a face
" is true.
Then, let's ponder about its impact
I can give examples of animation software and video games which are capable of generating random characters. Of course there are parameters, but, still.
If our mind cannot create faces, we could say that computers have beaten humans in creativity.
From another perspective without computers, we could infer that every fictional character would be based on a real living person.
Every painting/drawing/artwork featuring a face would be some kind of portrait.
Hm, as far as I know, we don't create faces. As far as I know, we see ppl in our dreams we have seen already. As you already said, our SC saves a lot of faces. All those faces return when you dream, I think the brain just fills a gap: "I need a face here, let's take that cashier guy from last Tuesday..." And yes, I believe we are able to mix them up...
Suppose that "just mixing up is not creating
Time to ponder about its impact
Consider that every language has a limited alphabet (set of letters). If you write a text in an existing language, you are just shuffling letters. This creates a permutation from the same set of letters. You are just mixing letters up. Therefore, writers (including poets) do not create anything, they just mix letters up. This post is just a permutation of letters.
Classical music composers use predefined notes that fit into a limited audible spectrum. There is also a limited set of octaves and a limited set of symbols to represent the duration of notes and pauses. When a composer writes a score for a music, they only choose a permutation of notes and timing. Then, they are just mixing notes (and pauses) up, not creating music.