The Architect of Hogwarts statue had such amazing detail on it. I loved the icons of the four houses around his feet, the lion, badger, snake and raven.
As an uber fan of the books I loved all the themed details in the castle such as the One Eyed Witch Statue(humpback witch) which as the previous poster stated, leads to an underground passageway between Hogwarts and the basement of Honeydukes in the books. They also had Mirror of Erised hidden in the dungon portion of the queue.
There was only one small thing wrong about the queue and obviously it only matters to the Potter nerds and that is the "kitchen" sign on one of the doors. I noticed it my first time through the queue and thought with a laugh, "Well only I would noticed that was wrong." Of course I then hear a guy behind me say, "Kitchen? Everyone knows that the kitchen is concealed behind a painting of fruit for crying out loud! You have to tickle the pear to get in. There is no door that says kitchen in Hogwarts!" His girlfriend just kept walking and mumbling, "there is also no glowing exit signs and handrails in Hogwarts either." It just cracked me up, because at least I didn't yell it out loud and get mumbled at for my nerdiness.