There are various instances where it's handy for the TD to get a random arena that isn't tied to a specific match, typically as a ranking match. In my case, we've needed it for a 3rd/4th ranking match, a tie breaker for our "Top Rookie" award, and a tie breaker for our "First Place (Women's)" award.

I'd like to see a button in Arenas or Rounds that draws an arena and displays it in a popup. Maybe a refresh/redraw button in that popup. In my case, just drawing from all active arenas, even if they're in-use for the current round, would be perfectly acceptable.