Potentially curious observation.
First image: tail cone, containing the APU:
http://cdn1.img.sputniknews.com/imag...1029478002.jpg
Second image: the rest of the tail:
http://cdn.thedailybeast.com/content...569.cached.jpg
Other side:
http://media1.s-nbcnews.com/j/newscm...-2880-1000.jpg
In the second image, you can see the line where the tail cone was attached. (We now have the entire tail except for HS and the rudder.)
The curious part is that the skin of the tail cone is badly sooted, but corresponding skin in the second image is clean.
This suggests that there was fire/smoke inside the tail, while the whole assembly was still in the air (and possibly attached to the rest of the fuselage), that's what caused the tail cone to separate (otherwise, I can't see a good reason why it would break off in midair), and the smoke was leaking out through the tail cone attachment line.
Note that there's no evidence of fire on the rear passenger door, so the fire was likely localized aft of the APB.
You can also infer the location of the APB from the third image. Parts forward of the APB have minimal damage, which could have been caused purely by ground impact. Parts aft of the APB are badly shredded as if by internal explosion.
However, I don't see how an explosion in that area could have caused the tail to break off entirely the way it did. It could have been the other way around. An explosion in an overhead bin (towards the rear, left side, judging by the fact that we're missing more skin on the left than on the right), causing decompression, causing the tail to break off, which severs the fuel lines to the APU, which leads to an explosion behind the APB that separates the tail cone and horizontal stabilizers, which land separately from the rest of the tail.