Did the Google version definitely come first? Looking through Google Reader blog, all I'm seeing is the textual "Google Reader Labs" logo with the chemistry beaker, until the 3D one appears in a desktop widget in May 2009. The OP's Flicker page is date June 2008. Anyone have earlier examples of the Google version?
My version was based on Google's 16x16 favicon. It was basically a scaled up version of that. Their "blocky" version did exist before, but mine was specifically a take on their favicon.