What does is mean to dream about painting a portrait?

Disclaimer: This answer is 100% subjective, my opinion.

Although many of Jung's descendents believe in a shared vocabulary of symbols of the unconscious, I'd have to say that to dream of painting a portrait depends largely upon how painting fits into your life. If the dreamer grew up with a father who was a portrait artist, that may be carry a different significance than from a dreamer who is a recent divorcee and is desperate for catharsis. It could mean to some, that it's finally time to quit their job and try something new. It could mean that you want to re-evaluate just who you are.