Pop stars can pretty much demand whatever they want. And Pharrell Williams wants a framed picture of Carl Sagan. The Smoking Gun got a hold of Williams' tour rider for his 2015 performances. And among the various specified food and drinks is the desire to have a protected picture of the late astronomer looking down on him with supposed kindly pride. The 42-year-old Williams has spoken of being obsessed with Sagan since watching the original "Cosmos" series when he was a child. The Sagan photo d…