What I'd like to see:
Mario: Wario colors replacing his brown and white colors.
Luigi: Dr. Luigi.
Peach: A Rosalina recolor (much like her Daisy recolor). Oh, and a classic SMB recolor (white dress).
Bowser: A "Dark Bowser" recolor, much like Link's Dark Link appearance.
Donkey Kong: A green color with the same fur tone as K. Rool's skin.
Diddy Kong: An outfit with him wearing DK's tie!
Link: The black or purple Melee Link costume returning (I'd side with probably the black). Oh, and his Skyward Sword look (specifically pre-Link wearing his green outfit) and Twilight Princess Ordon Village outfit.
Toon Link: Conductor Link colors. Also, a golden outfit, much like Link's golden outfit. A Melee Link-esk black outfit would be a nice touch, too.
Zelda: A Ocarina of Time child Zelda outfit, a classic (ALTTP) Zelda outfit, a Hilda recolor, a Skyward Sword look, and/or a Hooded Zelda outfit.
Sheik: A hooded Sheik appearance. Oh, and a more Melee-esk recolor of her original outfit.
Ganondorf: Two words: Green Tunic!
Samus: Light Suit, PED Suit, Dark Suit, and maybe a redone Fusion Suit. Basically, just upgrade her suits to look more like in her games, if possible!
Zero Suit Samus: Classic green hair, Other M short hair look. Oh, and a pure red outfit would be sweet.
Yoshi: If you could add anything, silver Yoshi would be it. Oh, and maybe give the black Yoshi Boshi's glasses.
Kirby: Various recolors from Kirby's Air Ride and recent Kirby games. Orange, brown, and black IMO would be awesome.
Meta Knight: Same as Kirby.
King Dedede: Same as above. However, I would like to see King Dedede in one of his alter ego outfits.
Fox: If anything could be added, it would be the Brawl recolors on Melee Fox.
Falco: Same as Fox.
Wolf: More Star Fox 64 outfits please!
Pikachu: More Party Hat recolors would be awesome! Oh, and a Raichu recolor (fur color), or a female Pikachu (the tail isn't pointy at the end).
Jigglypuff: More bow colors.
Mewtwo: A super black, a bright red, and/or a golden recolor!
Lucario: A Charizard Orange, a Purple color similar to Yoshi's purple, a Silver recolor (if possible), and a ruby red color would all make excellent recolors.
Squirtle: Pikachu yellow, default Squirtle Squad glasses Squirtle, golden Squirtle.
Ivysaur: Charizard orange, pure black, pure purple, golden Ivysaur.
Charizard: Arceus white, pure purple, golden Charizard.
Captain Falcon: Blood Falcon Emblem on his red outfit, a Samurai Goroh outfit/recolor, a Captain Falcon unmasked look, a golden outfit with a silver visor, and a dark purple Black Shadow-esk outfit.
Ness: Jeff's outfit, Poo's outfit, a more Ninten-esk outfit, and a Runaway Five t-shirt outfit.
Lucas: Give him his father's outfit. Oh, and get him a souvenir shirt from New Pork City!
Ice Climbers: Any outfit where you play as Nana instead of Popo. But colors that stick out to me: purple, golden, orange, light green (maybe neon green), silver, ruby, etc for their outfits.
Marth: All pink Marth (dat breast cancer awareness), golden Marth recolor, the old light blue Marth recolor coming back, and an orange outfit. Oh, and maybe a model based on his newer look.
Roy: A purple outfit (that majesty), Roy in his father's (Ephriam) armor, and a light blue Roy outfit recolor.
Ike: Radiant Dawn Ike with the same outfits (especially the standard outfit, gold outfit, green outfit, and red outfit).
Mr. Game & Watch: Purple, silver, orange, and white recolors.
Pit: A better Dark Pit look (maybe red eyes=???), a silver outfit, a purple outfit, a turquoise outfit, and a classic Melee trophy Pit look.
Wario: I doubt it is possible to add anything to him, but if I could, I'd give him a Masters of Disguise outfit, as well as a Mario, Luigi, and Waluigi recolor for both of his outfits.
Snake: Old (MGS4) Snake (with or without the eye patch), MGS1 Snake, Snake in a tuxedo, and Snake wearing his Sneaking Suit.
Olimar: Pink recolor outfit, black suit Olimar, and a pure white suit.
R.O.B.: Wii White, DS/3DS ROB (with DS/3DS eyes), PS2/3/4 colored ROB, and maybe PS1/x colored ROB.
Sonic: Super Sonic Gold, Shadow Black recolor, a Tails-esk colored orange/yellow (or whatever color that is), a pink (Amy Rose) recolor, and a purple (Big the Cat) recolor.
Yeah... sorry for my list being so long!!!!