First of all, great job! This was a delightful tale from Winky's perspective and it's always nice to see the house-elves playing a major role the way Dobby did in the books.
Second of all, there are some really insightful lines here, like this one: How strange, that the man he had killed should still be happy to talk to him, even in painted form. YES, THIS. How did all the other professors miss this? Did DD deliberately step out of his portrait every time one of them came into the office? Didn't anyone think it strange that he seemed at peace in his portrait over the man who murdered him? Thank you for pointing this out!
This line too, that other people have mentioned: She saw how he observed the other professors with a terrible look of longing in his eyes, like an elf who had been banished from its home but still watched its family from afar. Oh, my, yes. That was a terrible year for Snape, and I'm glad at least one other creature got to witness his true self.
Lovely job. A sweet little fic about loyalty and caring. :)