Hard Style. Either in game for something like Aram or Intro screen for new champion.

http://www.youtube.com/watch?v=Yl1gKUHeRxM

Seems to fit the having fun chaos theme that people tend to have with ARAM. Fun and energetic and a good way to make Aram more famous! xD

P.S, you dont have to listen to the whole thing, but I thought the intro was pretty nice and fits a "New Champion" kind of feel.

what about progressive instrumental power metal? Demetori is one of my favorite bands ever has some really epic stuff and isn't as offensive as Hardstyle or most other heavy power metal bands.

I feel the music should start off slow and build up over time. If its possible, it should start off quite calm and build up just as a teamfight or skirmish breaks out. But thats just my opinion, I know we all have different tastes when it comes to music.

Personally, I'd like to see something from Two Steps From Hell. But then, it is music - to each their own.

(I dont actually notice the music much as I'll be focused on whatever is going on.)