Fred just gets hit by a curse when there's a fight going on.
Dumbldeore gets hit with the killing curse and falls off a tower. lol
As for Hogwarts... well, when I read the book it was after having seen previews for the HP movie back in 2001, so I was never able to come up with my own image for Hogwarts or the characters. But I have my own picture of Harry/Ron/Hermione. Ron is almost the same in my head as he is in the movies, Hermione is a bit less pretty in my head, and Harry looks pretty different from older Dan Radcliffe.