Well given there will be 15 stages

1. Metropolis
2. Bat Cave
3. Fortress of Solitude/Phantom Zone

1. Atlantis
2. Arkham Asylum - housing unlockables in cells (Joker, Ivy, Catwoman, and Scarecrow) and interacting-cameo characters like (Riddler, Mad Hatter, Calendar Man) and 1 DLC unlockable Killer Croc in a HUGE cell which you only hear him until he's unleashed.
3. Oa
4. Themyscira
5. Aeaea Island (with animals all over the island)
6. Korll (Queen Bee's Hive would be wicked)
7. Star City
8. Injustice League Swamp Headquarters (we need some playgrounds for Swamp Thing/Poison Ivy)
9. Poison Ivy's Botanical Gardens (with a more gothic look)
10. Watchtower - with Hydroponics/Aquarium areas
11. Hall of Justice
12. Joker's Funhouse (practically an amusement park with his haunted house, would make a field day for Mirror Master in the mirror room)

I think they should have 2 characters/1 stage as a DLC Package sold together, which all 3 kinda go along with 1 theme. DLC Stages: (there probably won't be too many if any at all, yet interactions with backgrounds are a good chunk of this game's gameplay so it would be a fan-based want = $$$ that is if they turn out the way NRS wants them to)
13. Apokolips - I could see Darkseid and Mantis added to battle over the place, giving Doomsday, Parallax, or Anti-Monitor the boss-spots
14. Rock Of Eternity - I could see both Black Atom and Shazam as DLC with this, would make people wonder why Shazam wasn't there from the start and worry lol
15. Stonechat Museum (waterfountains would make great interactions, as well as being inside the museum itself, imagine Zatanna bringing the T-Rex skeleton to life, now that'd be pretty epic) I could see Gorilla Grodd and Killer Croc being perfect DLC to go along with this stage.

Well i'd rather see the east end than arkham asylum.But the joker's funhouse sounds good,i'm assuming it's the very same one he goes to in the killing joke?

Yeah I was thinking about stages vs interactions; it would be kewl if an inverted roller coaster went through the background and say Batman could use his hookshot to ride below it for a sweet kick to the nearby opponent's face; or let Poison Ivy make her own swing on the swing ride, with a beautiful round-about kick. Yet have Superman take both ends of a bullet-ride and smash the opponent between the 2 ends lol; Zatanna could bring the carousel to life; and Hawkman could pick up the opponent, fly them atop the tall hammer game and tie hang them atop it, then use his mace and smash the button sending the shock up to the opponent, lol that would be kinda comical/epic. OMG Flash could make them very dizzy on the teacups lol.

Another stage that would be well represented:

Slaughter Swamp - ressurection place of Solomon Grundy

Being a swamp could also allow special uses for: Killer Croc, Swamp Thing, Poison Ivy, Circe, Black Manta, and Aquaman.

Also.Inside the daily planet.How about it?

Hall of Justice

Legion of Doom HQ

Star Labs
And if there are any Static Shock characters, a City Park stage.