Display for 4 different cake on what kind of stand would you use? Please help

I don't understand what you are asking. You want to display 4 totally different cakes on one stand? Are they all the same size cakes?
Bakery Crafts has a group of 'single use' stands. They are foam and very sturdy that would work for you. You can get the 3 tier one and put the 4th cake on the table OR if still available get the 4 tier one. HTH (BTW: I've used the stand over & over if you get it back from the customer)
OR make yourself something like Wilton's floating tier stand. Use small styro rounds (like 6"ers - can cover w/fabrick, foil fondant etc or leave plain) and set up like a pillared cake one on top of another? Just throwing out some ideas