I would always try to future-proof your setup, especially if you are finishing off the ceiling/walls and it won't be easy to get into it later. As long as you have something sturdy to mounts your speakers to, you can mount them anywhere
I am loving this room, I have been dreaming about my HT room for years and these photos pretty much sum up what I have had in my head. Excellent job!! For those of you who want the dimensions in feet... 6.3 meters = 20.6692913 feet 3.7 meters = 12.1391076 feet 2.4 meters = 7.87401575 feet