Solari Diana and Lunari Leona (Reverse Concept)
I'm a big Diana and Leona fan (they are my main mid/support roles), and I was thinking that this would be a solid skin concept. I know its not that original, but the concept has been done before, ex: Reverse Annie. (I acknowledge that this is not my art and therefore am also not taking any credit for what is portrayed here.) I hope that i'm not the only one who has thought of this idea as well. I've had this idea for the longest time, but I've actually only gotten the courage now to share the idea which I was sure to have already been put out here on the forums.

edit 7/9/2015
ah yes this, it always comes up every 4ish months or so and just about every time it gets a riot comment saying it wont happen due to clarity problems
If clarity is an issue, then a concept to add to the skin that might help with clarity could be the idea of corruption. Both Diana and Leona have defected to their opposing sides, therefore leaving Diana's Solari abilities with a black/gold mix, black being from corruption obviously. With Leona's Lunari abilities, they could be colored a dark gray/silver chrome mix (emphasis on the dark gray/darker shades). I think this could differentiate the two a little better.