I mostly dream of people that I have seen before but I have also sometimes dreamt of faces that I do not recognize. I've always thought that they either represent people I've seen but do not remember or then that it's a mix of different faces that I've seen.

I also lucid dream every now and then, it's really cool even though it sometimes can be a bit scary. Last year I had a phase where I used to lucid dream that I was talking with my friends, and I remember saying to them in my dreams "isn't it strange that we can have a perfectly fine conversation even though I'm actually laying asleep in my bed?". But every time I said it the dream turned really strange, the other person would disappear and I would wake up. I think it happened because saying it made me realize that the other person wasn't really there and I was actually talking to an aspect of myself.

Anyhow, really great post and the subject is fascinating! :)