At least put in Gerald, Valerie, &/or Clyde as far as Black characters go. Not to mention El Tigre & Ronnie Anne regarding Latino characters. But otherwise, not a terrible list. I guess Fairly Odd Parents (& by extension, My Life as a Teenage Robot) does have legal red tape blocking Timmy from getting in. Cool to have Zuko, but he isn't really a big surprise. And Susie's how an option since Tommy is getting in.
Source: Nickelodeon All-Star Brawl files (posted by Nick All Star Brawl News on Twitter)