Curated by Al Globus, the collection of renderings are really fantastic. You should check out Mr. Globus' site he has a lot of writings on the subject.
"For me the single overarching goal of human space flight is the human settlement of the solar system, and eventually beyond. I can think of no lesser purpose sufficient to justify the difficulty of the enterprise, and no greater purpose is possible."
Mike Griffin, former NASA Administrator, in 2004 testimony before CongressPretty cool.