The only 2 (or 3) things that i think that a skin referencing that should have are: Poses and Muscles (and maybe Stands).
Poses are related to the animations of the champ and maybe the splash art... And the muscles are something directly related to the champion itself, not the skin. Considering that i cant see a whole skin line based on that... sure, maybe a recall animation or a dance, but nothing more than that.
https://i.ytimg.com/vi/qMDXTvueHKs/maxresdefault.jpg
I mean, look at the JoJos, they dont really share an strong thematic aside from the things that i said before (poses and muscles)... Its not like the magical girl genre that has a lot of things that define it regarless of the anime.
http://www.calabozomutante.cl/wp-content/uploads/2017/09/evolution_of_the_magical_girl_by_shattered_earth-d4sskij.jpg
I mean, lets imagine that Riot releases a skin with... i dont know, taric having a similar hairsyle to Josuke... then it wouldnt be a reference to Jojo, but a reference to that weird Rockabilly style instead
http://www.hairstyles123.com/hairstylepics/rockabilly/rockabilly_hairstyle_8.jpg
Or if its a reference to Jotaro... then the skin like would be a reference to the school uniform of the japanese students(.... i think)
http://www.japanblogger.com/image-files/elemgakuran.jpg
Maybe... a School Academy Taric skin that makes a jojo pose when recalls?