Like maybe fireworks over Org and Stormwind or something and a server wide message to everyone from the devs.
Again, I know it's totally unnecessary and more work for the devs for something that will last ~10 minutes, but it would be a nice last memory of the server for all of us. The FFXIV and SWG shutdowns are what made this come to mind. Both of them were completely unnecessary, but turned out to be very memorable moments. Seeing as though every argument I make for Nost involves the memories I made on here I just feel it'd be really fitting for the end of the server to be one of those memories as well. And not just memories of everyone going to Blizz to yell at them or bickering between other private server communities about where we'll all end up, but something kinda bittersweet where we're all together online on Nost for one final time.
I guess it seems weird to do that for a private server since the world itself still lives on in other servers, but Nost is and will probably forever be the largest private server to exist so its kind of a special case here.
Hell, maybe the Nost devs will pull a FFXIV and come back two years later, but as an official Legacy server

