Blood. The more, the merrier.

My biggest suggestion would be to increase the weight and impact in which spells have on a champion - making it more pleasurable in both dealing damage as well as successfully killing your opponent.

Now without spending resources and changing each animation, this could be done by adding more blood within the game, blood that perhaps could smear against the environment when damage is dealt. Whether the blood stays there, or disperses over time would be up to debate. Perhaps even design different color/types of blood depending on the champion.

I am not aware of how games are rated, or the degree/amount of blood needed that would change the rating from Teen to Mature - which I imagine RIOT would be against. Nevertheless, I believe it would increase the overall experience.

Kawa