Expect the unexpected idea
While trying to figure out how many people to send through at a time in our haunt, today this triggered an idea. Let's say that a group of people are walking through a hallway and dropping from above is an animatronic man including flailing arms and thrashing moves. Startling as this is, 3 of the 5 or 6 people actually get the impact. The animation goes back up and the people pass looking for the animation to drop again. My idea is this: The dangling man goes up after scaring people, then switches into another animation. For example, since the people know that something is above them why not let a giant spider fall on them. The scare is something people expect but then the switch of one animation for another they don't. This idea might be a nice idea for longer lines. Another example would be the drop panel portrait. The monster's head could rotate around each drop to switch up the scare. One drop he's a scary dead-guy and on the next he is a rotting wolf creature.
Just some food for thought.