Hello! Here is a pic of our beloved Potions Master, now taking a swing at Defense Against the Dark Arts! Harry's expression shows how skeptical he is about Snape's loyalties..I guess. Ron isn't exchanging glances with Harry... actually he looks kinda like me in my classes when I'm utterly bored. And, of course, Hermione is paying complete attention to the teacher.

I'm sorry if my paintings on the walls don't do the description justice... Or if they disturb you in anyway.

"Your defenses," said Snape, a little louder, "must therefore be as flexible and inventive as the arts you seek to undo. These pictures" -- He indicated a few of them as he swept past -- "give a fair representation of what happens to those who suffer, for instance, the Cruciatus Curse" -- He waved a hand toward a witch who was clearly shrieking in agony -- "feel the Dementor's Kiss" -- a wizrd lying huddled and blank-eyed, slumped against a wall -- "or provoke the aggression of the Inferius" -- a bloody mass upon the ground.

-Harry Potter and the Half-Blood-Prince, by JK Rowling

Heehee...The title's funny when you think about it...
(Dada, if you don't know, is a movement "which concentrated its anti war politic through a rejection of the prevailing standards in art through anti-art cultural works." -Wikipedia def...
Or, if you didn't get that, it was a period where artists and others tried to shock people with their "anti-art"....Or just look it up yourself...I can't explain.)