I like this "game" much, but i can play it only for worlds, so i now i'm writing this with the hope you will vote>Riot will see it>And they make it each split.
About the rewards: the icons are enough. Only for playing the game you get a "pick'em" icon,but If you make everything correctly you will get a 3 icons with teams who where participating the split/event:
The 1st place team+2 by your choice.
Time- 1 week before the split/event to the start of the 1st game.
You will have access only to the split/event that's connected with your region.
If you want the game vote +1, if you don't want it just don't play it.