Take a lesson from Master x Master and improve your lobby system.
Master x Master may be a dead game and most people probably never even heard of it, but there are several things I think Riot needs to take a look at from Master x Master's game that should be added to League of Legends.
Currently on League when sitting between games you are just sitting around with the ability to send messages with a chat box, nothing really else other than purchases. However on Master x Master, you actually interacted with people outside of game. People you never met before even in game. You could actually meet random people and chat with them with the ability to walk around as any character you choose.
Imagine walking around as your favorite league character in a lobby system where you can que up for normals, ranked or PvE (Master x Master had amazing PvE boss battles). That's what I want to see from riot games. A lobby system like this and more PvE content which they obviously borrowed from this game already.