I know it can be difficult, but try to visualize a person’s face that doesn’t belong to anyone you know or have seen. And make the features reasonable, the nose not too long for example, so that such a face is feasible. Given that the world’s population is estimated to be just over 6.4 billion as of july of this year, there ought to be someone who is alive today who looks very much like the face you have imagined from scratch. It might be a closed circuit system, by which I mean that any feasible face we can conceive of is the face of someone alive today.