Additional end game stats
It'd be nice to see "Shields provided" or something similar. Maybe "Damage mitigated for others."
Other ideas for end-game stats that I've had include "Damage reflected" so when I play rammus I can lol. Largest heal, largest crit would be cool to see at the end screen. Highest damage burst taken and survived. There are so many metrics in this game, the list at the end game screen could be so much more detailed.
Also... how hard would it be to implement a "Play of the game" kind of thing? Serious question, I honestly don't know if it'd be difficult or not.