Pop star Tristana Concept
http://sayomi96.deviantart.com/art/Popstar-Tristana-652060335
it does not look like Popstar Ahri. i know it Ahri's skin is inspired by a song that called "Genie" here is a shot of it:
http://data.whicdn.com/images/3054112/large.jpg
but this Tris is based on another song by same artist called "Oh!"
http://orig03.deviantart.net/f149/f/2012/090/4/a/snsd___oh__by_azularosa-d4uk6yl.png
i use this theme for Tristana because why not? Nobody says it must be the same for other Popstar skins :D