Heres all the scrapped levels I had (they were scrapped for the reason in my comment)
A deserted temple with a bunch of traps
A sublevel of Level 7 and 8 which is a flood escape
An elevator which takes you to randomized scenes
A construction site (I don't remember that much of this so that's all you get)
A hallway with doors that lead into rooms with optical illusions (don't steal this idea cus I had this idea recently and still might make it)