Well, from what I know, here are the stages that are legal, counterpick, and banned from tournaments.
LEGAL
- Battlefield
- Final Destination
- Yoshi's Island
- Lylat Cruise
- Smashville
- Pokemon Stadium (Melee)
COUNTERPICK
- Delfino Plaza
- Luigi's Mansion
- Mushroomy Kingdom (Above/Under)
- Mario Circuit
- Bridge of Eldin
- Pirate Ship
- Frigate Orpheon
- Halberd
- Pokemon Stadium 2
- Port Town Aero Dive
- Castle Siege
- Summit
- Skyworld
- Hanenbow
- Shadow Moses Island
- Green Hill Zone
- Yoshi's Island (Melee)
- Jungle Japes (Melee)
- Onett (Melee)
- Corneria (Melee)
- Rainbow Cruise (Melee)
- Green Greens (Melee)
- Brinstar (Melee)
BANNED
- Rumble Falls
- Norfair
- Spear Pillar
- WarioWare, Inc.
- Distant Planet
- New Pork City
- 75m
- Mario Bros.
- Flat Zone 2
- Pictochat
- Temple (Melee)
- Big Blue (Melee)
I found these out on Brawl Central. I don't know if we are going by real tourney rules but I think we should not play on banned stages listed above. Legal stages are fine. Counterpick are fine as well but I think Legal stages can be picked over counterpick stages easily or something like that.