Reminds me of one of my sayings.
Hunter's Hundred Eighty-Sixth Rule: If you look back and there's folks behind you, you're either a leader or about to get mugged. Not that there's much difference.
Here's a couple more thoughts. Set the date for something like this a couple weeks out. Formally invite the Supergroups and other "leadership" of each server to get together to organize their server's pageant. Make sure some effort is made to demorecord each parade - multiple "cameramen" would be best.
And finally, issue a formal request that any devs or former devs who wish to participate be included as "marshal" - a different one on each server if possible. If they can't arrange to be there, at the very least this would give a great use for those "real life developer" costumes people did for the Unity rally. My thought here is that we should make this a parade / pageant that celebrates the accomplishments of the community over the past 8 years.
We shouldn't do any judging, though having CC after the parades which ARE judged would be appropriate. The notion is that this is not a competition between the servers, but a community wide event where everyone is asked to show their pride in what we've built. The final darkness may (or may not) be looming, but we still all have a lot to be proud of. Kind of a Paragon City Thanksgiving Day Parade.... (wink). Not that I am suggesting waiting that long, of course.