Definitely Not Diana Skin
I think that Diana is a character that doesn't really have much of a fun side to her. The skins that she does have are all dark and brooding. Even the Infernal skin, while less dark, still felt like it wasn't a skin that fit her very much. It felt more like, "Well, we have this extra Infernal Paint. Uh...we haven't done anything with Diana for a while. Sigh Fine.". And that was that.
My suggestion would be a Definitely Not Diana skin, where, rather than the trench coat and Groucho Glasses, she would try to impersonate the ranks of Leona. She would still have her sword and abilities, but she would have different armor on in an ultra-faded yellow motif that shows her trying to add color to an existence that is solely black and white. She would have make-up on that you can tell was not placed by someone that wants to be bright, warm, radiant. I think that would be cool to do and true to the feel of the character.
Anyone have ideas on how to make this better?