I like interpreting, so I'll make a guess too. To me it seems like a cathartic tool to bring out feelings about social happenings that we don't understand or that happen very quickly. Its not about death, love, growing old or money and not even really about religion. It is about rapid change in the world, but a change that is not change but the turning of a huge wheel. Its also about the fear of the people of the world that things could go awry, but it sees the world as a cycle as if its troubles were just par for the course. Jesus on the boat represents the world as we are familiar with it paddling towards the land of the dead. That image comes up repeatedly, so I think its the main theme. The other symbols might represent experiences that society has gone through or must go through again.