Not to belittle from the fact that innocent soles have died and been injured, god help them all and their relatives and friends.
But there is nothing we can tell about the size of the explosion from the photos shown above. The vast majority of the debris I see are ceiling tiles, these only weigh a few ounces each and are not fixed, they simply lift and slide out for easy access. A very large percussive firework could unseat and bring down many tiles. Other more substantial items, like departure boards seem largely unaffected.
Not that I am saying the explosion wasn't large, just that the pictures themselves don't prove it.