I haven't seen one either.
This was my first year being active "on stage." I did make a deal with Mercenary when I booked them.
Glenn: Mikkel, "You play a cover song that I pick out and I'll take a dive." Mikkel: Which One?
Glenn: Cowboys from Hell
Mikkel (after 24 hrs): You are on!
As for Thunderstone, Nino actually saw a post I made on this forum that threatened to jump up on stage and sing "Forth Into the Black" and that I would be totally pissed if they didn't do it. They grabbed me on Saturday and said "You are doing it."
As for Evergrey, I was down front and Tom told me to get my ass up there. I obeyed.
While I had a blast doing all that, it's not going to become a habit. I'll pick my spots when the time is right though.