A book series?
A book series that coincides or pre-dates LoL would help flesh out the game and help create a sense of storyline progression. But we have to consider the fact that something as big as that will cost a lot of money and for a Free to play game such extra expenses would be very hard to cover. One way to approach this problem would be to ask the community to help sponsor this project by using a crowd funding platform such as Kickstarter or Indiegogo. It's my love for books that makes me post this :D