De acordo com a resposta do rems a este pergunta , JK Rowling já respondeu.
Q: All the paintings we have seen at Hogwarts are of dead people. They seem to be living through their portraits. How is this so? If there was a painting of Harry’s parents, would he be able to obtain advice from them?
JKR: That is a very good question. They are all of dead people; they are not as fully realised as ghosts, as you have probably noticed. The place where you see them really talk is in Dumbledore’s office, primarily; the idea is that the previous headmasters and headmistresses leave behind a faint imprint of themselves. They leave their aura, almost, in the office and they can give some counsel to the present occupant, but it is not like being a ghost. They repeat catchphrases, almost. The portrait of Sirius’ mother is not a very 3D personality; she is not very fully realised. She repeats catchphrases that she had when she was alive. If Harry had a portrait of his parents it would not help him a great deal. If he could meet them as ghosts, that would be a much more meaningful interaction, but as Nick explained at the end of Phoenix—I am straying into dangerous territory, but I think you probably know what he explained—there are some people who would not come back as ghosts because they are unafraid, or less afraid, of death.
fonte da citação Accio, Edinburgh Book Festival, 2004
Para resumir, digamos que pinturas são como memórias. Pessoas em pinturas só podem "repetir frases de efeito", porque deixam uma parte de sua aura por trás delas, e apenas em lugares altamente relacionados a elas. Então, sim, de certo modo, eles deixam algo que pode ser assimilado a "uma parte de suas almas", mas isso é tudo. Eles podem dar alguns conselhos, mas nada que você não possa lembrar ou esperar deles.