Our Top 4 was Friendship is Magic, Mario, Legend of Zelda, and Homestuck
I suggest Rarity, Celestia, Luna, Discord, and Spike for FiM. Toad, Daisy, Waluigi, Bowser Jr., and idk... Donkey Kong?. For Zelda, I'm thinking of having Skull Kid return, and you guys can try to choose the 4 others. And as for Homestuck have Dave return. And add John and/or Jade and some new trolls in.
For FiM, Spike and Discord are definitely good.
Mario: Uh, really, I don't care too much.
Loz: Also don't care, maybe Lord Giriham.
Homestuck: VRISKA, Doc Scratch, Dirk (being Bro, he is automatically awesome)