It depends on your jurisdiction
In the UK there is an Act of Parliament that specifically restricts what you can do with images of Princess Diana, but in general you can do what you like with the images of dead people, as far as I know ... which isn't very far and I wouldn't be the slightest bit surprised if they've changed the law recently without telling me.
Incidentally, there was a case in which a US company that was selling images of Princess Diana was sued by the UK organisation that "owns" her image. The UK organisation lost, if I recall correctly. So you can sell images of dead people without authorisation in some cases, even in the US.