Not related to the mockup, but while you're looking at the thread - have you thought about making appleseed bittorrent-distributed instead of diaspora-distributed? In other words, no server at all, just a swarm of computers storing the social graph data, photos, comments etc. between them with some amount of replication?
I actually don't think that's practical, at this time. Diaspora originally started out with that goal, but quickly moved over to the same server-to-server approach that Appleseed had been using.
Just adding the required usability to allow single-users to administer a social networking instance adds a whole ton of complexity to the software. Way more than something like Bittorrent.
I think it's possible, at some point, but for now, I think a more conservative server-to-server approach is necessary.
