Just wanted to post my Theme List for everyone to see!...Enjoy!
Alpha Flight: Guardian, Sasquatch, Arachne and Wolverine(Any.)
A-Next: American Dream, Spider-Girl, Ant-Man, Captain America(Regular), Hawkeye(Either), Scarlet Witch, and Vision.
Avengers: Too many to name!!! Pretty sure you already know enough ;d!
Avengers Academy: Ant-man(Or Giant-Man), Tigra, Quicksilver And Reptil.
Avenging Host: Dr. Doom, Giant-Man(Or Ant-man), Hawkeye(Either), Iron Man(Any), Daredevil(Either), and Phoenix.
AvX: Two players are Avengers, and the other two are X-men.
Brotherhood of Evil Mutants: Magneto, Scarlet Witch, Rogue, Beast(For dark beast), Havok, Psylocke, Quicksilver, Classic Wolverine(For Daken), and Sabretooth.
Cabal: Dr. Doom, Emma Frost, and Dark Iron Patriot.
Cap Corps: Avengers Captain America, Captain America, Super Soldier Captain America, American Dream, and Bucky Cap.
Champions: Angel, Black Widow, Ghost Rider, Luke Cage, Goliath, and Ice-man.
Civil War: Two players are heroes from Ironman's side, and the other two heroes from Cap's side.(You can also do Civil war Ironman's side where everyone is a hero(Or villain >:>) from ironman's team....Or Civil war cap's side ;p)
Classic Defenders: Silver Surfer, Doctor Strange, and Hulk.
Dark Avengers:Dark Iron Patriot, Sentry, Venom, Classic Wolverine(For Daken), Red Hulk or Gladiator Hulk(For Ska'ar), Scarlet Witch(For June Covington) and regular Hawkeye(for Bullseye).
Dark X-men: Angel(For Mimic), Beast(For Dark Beast), Dark Iron Patriot, and YUP! you guessed it! Classic Wolverine(For Daken.).
Defenders: Doctor Strange, Hulk, Silver Surfer, Valkyre, Hawkeye, Luke Cage, Daredevil, Thing, Ant-man(Or Giant man), Black Cat, Moon knight, Ms. Marvel, Wasp, Black Panther, Ghost Rider, Beast, Vision, Mr. Fantastic, Scarlet Witch, Captain America, Wonderman, Captain Marvel and Spider-man.
Ends of the Earth: EotE Spider-Man, Doc Ock, Black Widow, and Mysterio
Exiles: 2099 Spider-Man, Psylocke, Shadow cat, Rogue, and Gambit.
Fantastic Force: She-Hulk, Human Torch, and Black Panther.
Fantastic Four: Mr. Fantastic, Invisible Woman, Thing, and Human Torch(You can also use Spider-Man or She-Hulk)
Future Foundation: Mr. Fantastic, Human Torch, Invisible Woman, Thing, Ant-man, Future Foundation Spider-Man, Future Foundation Dr. Doom, and She-Hulk.
Force Works: Iron Man(Any), War Machine, Scarlet Witch, Avg Captain America(For U.S. Agent),Wonderman and Arachne.
God Squad: Thor(any), Silver Surfer, and Black Panther(For Panther God).
Great Lake Avengers: Mr. Fantastic(for Flatman), Hawkeye, Deadpool, Squirrel Girl, and Hulk(For Big Bertha)
Heroes for Hire: Ant-man(ONLY), Black Cat, Black Panther, Black Widow, Luke Cage, Deadpool, Elecktra, Falcon, Ghost Rider, Hulk, Moon Knight, Punisher, She-Hulk, Spider-man, and Spider-Woman.
Hulks!:Hulk, Indestructible Hulk, Red Hulk, She- Hulk, Gladiator Hulk, Avengers Hulk, And Red She-Hulk.
Illuminati: Beast, Black Panther, Doctor Strange, Ironman(Any), Mr. Fantastic, and Captain America.
Invaders: Super Soldier Captain America(Or Reg), Bucky Cap, Human Torch(For the android one), Hawkeye(For Union Jack), and Avg Captain America(For U.S. Agent).
Lady Liberators: Black Widow, Valkyre, Invisible Woman, She-Hulk, Spider-Woman, Storm, Scarlet Witch, and Wasp.
Legion of Monsters: Ghost Rider, Werewolf by night, Morbius, and Punisher(For FrankenCastle).
House of M(Luke cage's team): Luke cage(Of course..), Hawkeye, Moon Knight, Tigra, and Black Cat.
Marvel Anime(Credits to Benfromcanada): Blade, Wolverine, Monkey King, Cyclops, Storm, Beast, and Ironman.
Marvel Knights(Ultimate): Daredevil, Doctor Strange, Moon Knight, and Spider-man.
Marvel Zombies: Wolverine, Luke Cage, Iron man, Hulk, Giant man(Or ant-man), and spider-man.
Midnight Sons: Doctor Strange, Blade, Morbius, and Ghost Rider.
Mighty Avengers: Iron man(Any), Ms. Marvel, Wasp, Black Widow, Sentry, Spider-Woman, Ant-man, Avg Captain America(For U.S. Agent), Vision, Wonderman, Quicksilver, Doc Ock(For Superior Spider-Man. XD), and Scarlet Witch.
Movie Avengers: Avengers Hulk, Avengers Nick Fury, Avengers Black Widow, Avengers Hawkeye, Avengers Iron man, Avengers Thor, and Avengers Captain America.
Mutant X: Captain America, Ice-man, Havok, and Gambit.
New Avengers: Iron man(Any), Captain America, Luke Cage, Spider-Man, Wolverine, Sentry, Spider-woman, Doctor Strange, Hawkeye, Bucky Cap, Ms. Marvel, Thing, Squirrel Girl, and Daredevil.
New Defenders: Angel, Beast, Iceman, and Valkyrie.
New Fantastic Four: Hulk, Spider-Man, Ghost Rider, and Wolverine.
New Warriors:Scarlet Spider(Either), Nova, and Firestar.
Original Avengers: Ironman(Any), Thor, Wasp, Ant-Man(Or Giant man), and Hulk.
Original Super hero Squad: Iron man(Reg), Silver surfer, Thor(Classic), Falcon, Wolverine(Reg), and Hulk(Reg).
Original X-men: Cyclops(Reg), Iceman, Jean Grey(Reg), Beast, and Angel.
Phoenix 3!?: Emma Frost, Colossus, and Ast. Cyclops.
Revengers: Wonderman, Venom(For Anti-Venom), Classic Wolverine(For D-man), and Goliath
Secret Avengers: Captain America, Beast, Black Widow, Valkyre, Moon Knight, War Machine, Ant-man(or Giant man), Nova, Hawkeye, and Black Suit Spider-Man(For Flash Thompson).
Secret Defenders: Doctor Strange, War machine, Wolverine, Ice-Man, Arachne, and Ant-man(ONLY!).
Sinister Si-Er...Four.: Venom, Mysterio, Green Goblin, and Doc Ock.
Super Hero Squad: Scarlet Witch, Reptil, Wolverine(Reg), Silver Surfer, Hulk, Falcon, Thor, and Iron man(Reg).
Spider-Friends: Basically any Spider-related hero.
Spider-man and his Amazing Friends!: Spider-Man, Iceman, and Firestar.
The...Four!?: Cable, Cyclops(Regular), Iceman, Magneto, Jean Grey(Any), and Storm
Thor Corps: Thor, Ultimate Thor, Valkyre, Classic Thor, Battle Armor Thor, and Avengers Thor.
Thunderbolts: Hawkeye, Dark Iron Patriot/Green Goblin, Venom, Ant-man, Black Widow, Luke Cage, Gladiator hulk(For Ska'ar), Deadpool, Elecktra, Punisher, and Red hulk.
Uncanny Avengers: Captain America, Avengers Rogue, Havok, Avengers Wolverine, Thor, Wonderman, Wasp, and Scarlet Witch.
Weapon X: Deadpool, Wolverine, and Sabretooth.
West Coast Avengers: Hawkeye(Either), War Machine, Tigra, Ant-man, Moon knight, Scarlet Witch, Wasp, Vision, Avengers Captain America(For U.S. Agent), Wonderman and Arachne.
X-Factor: Iceman, Angel or Archangel, Quicksilver, Mystique, and Havok(Only doing certain members so it wont just be another X-men Team.)
X-Force: Cable, Deadpool, Wolverine, Colossus, Psylocke, Storm, Archangel, Cyclops, and Nightcrawler(For the AoA version.).
X-men: Too many to say, pretty sure you already know some XD.
All New X-men: Kitty's group: Shadowcat, Beast, Iceman, Storm, and Avg Wolverine.
All New X-men:Cyclops's Group: Modern Cyclops, Magneto, Emma Frost, and Angel(No, you can't be Arch Angel. XD)
70's X-men: Nightcrawler, Wolverine, Colossus, and Storm.
80's X-men: Shadow Cat, Rogue, Magneto, and Psylocke.