OK so it's not human sculpture, but it is sculpted by centuries of water and various dissolved compounds slowly. I haven't a clue geologically how beads of stone have formed.
Good question! The figures on the bottom in the silhouettes are from rocks in front of the light. Since these lights are the only source of illumination for the entire cave, everything else appears black.
The world is changed. I feel it in the water. I feel it in the earth. I smell it in the air. Much that once was, is lost, for none now live who remember it. -Lord of the Rings, The Fellowship of the Ring