What was changing in the temple

I won't spoil too much because I will tell you this based on a clip I watched because I haven't seen the movie yet. It seems the alien frescos on the ceiling start decomposing to the contact of the atmosphere.

You can watch the clip here. It's clip# 3 http://thefilmstage.com/news/prometheus-gets-new-imax-poster-and-four-clips/

Good question. We don't truly know why. It started once the atmosphere changed in the room upon the crew entering it. The Mural of the humanoid painting was what was changing. We're still unsure - but a guess could be that the Mural was changing to depict the next stage in the Alien life cycle. To further clarify what I mean - the initial Mural was of an Engineer (I assume) doing something. My guess? Being punished. I see a gaping hole in his side (Like the Titan Prometheus) - perhaps this was the first step in solving the mystery. This Engineer did something he wasn't supposed to and to punish him, the other Engineers created a creature which would torture and punish him in the most excruciating way. (Bursting from within) Perhaps the Mural was changing into the next phase of the punishment - unleashing of the destructive Bio-Former to whoever trespasses in that temple room. It's my most viable theory at this point.