One thing I really enjoyed about DotA All-stars is that, even though they were WC3's voices, clicking your hero several times would result in "annoyed" quotes that often ended up being hilarious, witty, or overall humorous.
Do you think we could have some similar character interaction in LoL? The thing I'm thinking is maybe they could even be built in to trigger on some events like your champion killing a bunch of heroes: after the tournament voice finishes, a brief pause occurs, and your selected champion could say something witty or funny such as Veigar going on about how size doesn't matter when you've got infinite knowledge. Or Annie saying in her cute, evil voice how much fun it was playing with the people she killed!
I really enjoy it when you can interact in the characters in such a way. They also did something similar in Team Fortress 2 where the in-game characters really love to interact in all sorts of ways and it makes for some splendid moments of gaming.
EDIT: If there's a situation where multiple characters are 'owning' or somesuch, maybe add in a pause between each character's line so they don't get mushed up into one jumble of voices!