Wonderful post with excellent information.
While I do find the current artwork to be quite attractive in its own right, I understand the marketing need to create something more distinctive and simplistic then our venerable gray blob. That being said I do like the designs that @josheah has made (favoring the double helix on the starry background myself).
I'd also totally be down for purchasing a commemorative coin for the millionth block if they end up getting made.
Plans for the commemorative coin were discussed in a meeting last night - I'd expect to see a post appear in the next few days detailing what form this will take. Also glad you like the designs for the logo!