Many people are confused why there wasn't any mention about Snape portrait in Headmaster's study when Harry came there after Voldemort's dead. Snape after all was a Headmaster of Hogwarts so there should hang his portrait after his death, shouldn't it?
When Dumbledore died, his portrait appeared there at once.
So didn't Harry just noticed Snape portrait or there wasn't any? If latter - why not?