If you are looking at speakers like the MK SS150, then mounting them, and selecting the proper or most effective placement are the only problems.
M&K SS150/BLK - Dream Home Cinema
if you feel you can mount the speaker adequately to your ceiling, and if you can place them effectively. Then I don't see a problem.
I'm curious if this is going to be a 5.1 or a 7.1 system?
How big is the room? (dimensions)
Is there are reason why you can't wall mount the speakers?
The question isn't - can they be ceiling mounted, the question is - can YOU ceiling mount them? Given that they usually HANG on a wall, you are going to need an effective plan to securely Ceiling Mount them.
Though I don't know the difference in price, but I suspect, these speakers would be just as effective Ceiling mounted and a lot more shallow -
MK Sound MP-150 On-Wall Speaker | High End MK Sound Speakers | Moon-Audio.com
MK Sound SS-150 THX Tripole - Surround Speaker | High End MK Sound Speakers | Moon-Audio.com
Given the distance to the ceiling, and depending on the placement, I'm not really sure you need Di/Bi/Tri-Pole speakers. I would say the Di/Bi/Tri-pole would work better along the side in a room that has multiple rows of seating. If a normal lounge with a single row of seating, and depending on distance and placement, the M&K MP-150 would work fine.
So, can they be ceiling mounted - Yes. Can YOU safely and effectively ceiling mount them is impossible for use to say.
Steve/bluewizard