[Spoiler? I know the end of the series is almost ten years old but just in case...]The portrait is of Professor Snape, who killed Dumbledore and appeared to be evil; as the final book proved, this was not true, but I guess not too many at Hogwarts knew the truth, as it is described as a controversial move.
There are two short biographies at the end, about Professor Trelawney and Syvanus Kettleburn (I wasn't sure who this was - he is Hagrid's predecessor). There were also some fascinating insights into other aspects of wizadry, with my favourite being the essay on polyjuice potions.
I was surprised not to see anything about Sirius Black in this e-book, but maybe JK will publish some more; we need biographies of Snape, Hagrid and Dumbledore too, but maybe I should check out Pottermore again.
Next book: The X-Files Issue 6 (Joe Harris, Matthew Dow Smith & Jordie Bellaire)