FYI you can only make stacks of crates 8 crates high, you can also have four madame leota tables with four crates on top
i also know you can put at least four rugs on top of each other but i was running out of credits so could not keep testing

I know that ice cubes u can stack at least 5 ( i gave up after that)

it actually depends on what room you are in. - each type of room has different dimensions upward as well as length and width.

in space room were u see those rides u can stack i think atleast 7 tables bc i did but im not sure but i am sure it was more then 4