Here is a list of all confirmed characters and pictures to go with them. This list will be updated as new characters are announced.

Veterans

Mario
Stars in Mario games
First appearance: Donkey Kong


Link
Stars in Legend of Zelda games
First appearance: Legend of Zelda


Kirby
Stars in Kirby games
First appearance: Kirby's Dreamland


Pikachu
Stars in Pokémon games
First appearance: Pokemon Red / Blue


Fox
Stars in Starfox games
First appearance: Star Fox / Star Wing


Samus
Stars in Metroid games
First appearance: Metroid


Zelda
Stars in Legend of Zelda games
First appearance: Legend of Zelda 2


Bowser
Stars in Mario games
First appearance: Super Mario Bros.


Donkey Kong
Stars in Donkey Kong games
First appearance: Donkey Kong


Yoshi
Stars in Mario games
First appearance: Super Mario World


Peach
Stars in Mario games
First appearance: Super Mario Bros


Ice Climbers
Stars in Ice Climber
First appearance: Ice Climber


Newcomers

Pit
Stars in Kid Icarus games
First appearance: Kid Icarus: Of Myths and Monsters


Metaknight
Stars in Kirby games
First appearance: Kirby's Dreamland


Zero Suit Samus
Stars in Metroid games
First appearance: Metroid: Zero Mission


Wario
Stars in Mario, Wario and Warioware games
First appearance: Super Mario Land 2: Six Golden Coins


Snake
Stars in Metal Gear games
First appearance: Metal Gear


Ike
Stars in Fire Emblem: Path of Radiance
First appearance: Fire Emblem: Path of Radiance


Pokemon Trainer
Stars in Pokémon games
First appearance: Pokémon Red / Blue


Diddy Kong
Stars in Donkey Kong games
First appearance: Donkey Kong Country


Lucas
Stars in Earthbound games
First appearance: Mother 3


Sonic
Stars in Sonic The Hedgehog games
First appearance: Sonic The Hedgehog


King Dedede
Stars in Kirby games
First appearance: Kirby's Dreamland



I will add information about the characters, skillsets and Final Smashes at a later date.