I love the photos so keep them coming.
Do we have an idea of which way the valve stem was launched through the floor and into the ceiling panel. The trajectory might give an idea as to whether the bottle was loose or in place at the time. I'm guessing that a + or - 15 deg cone angle trajectory would be inconclusive, but if it was greater it might be a significant pointer.
I am also reminded that we still don't have a reason for the very large hole in the fuselage, without lesser shrapnel damage holes visible.
The ATSB certainly has their work cut out for them to identify the cascading damages as well as the chicken and the egg.