Level Structure

[Yelhsa]

Does anyone know how I can have the bottom and top floors show simultaneously without the ceiling like this?
or when putting in stairs like this?

[Theraven]

There's a setting in the graphic details - "show hidden items" or something like that. If you combine that with the cameraman mode, it's not hard at all

Walls up/down can be controlled by home/end on your keyboard, and floor up/down by page up/page down. While in cameraman mode, the camera won't jump to the next floor but stay put, so you'll see all the floors that fits into the screen.

I  don't think it's possible to do this properly with the play mode camera, so it's mostly useful for screenshots or such.

[XPTL297]

If you are only wishing to take pictures, I don't think that the ones you show are having any special trick. I always take pictures this way and for the purpose I Build the house already with smaller rooms (like the one where the burglar is punching) as open room over a two etage high house that has no floor between them. So, this is not a trick but special constructions. If you place the camera on the second floor and there's no floor beneath, you will see both floors simultaneously.