I'm surprised why Yasuo hasn't got a fitting skin to his theme. Most are edgy skins, which are nice but I feel a theme one would be great and Sakura petals fit him really well wearing a Kimono and a japanese sun hat
Here's a few images for ideas;
Outfit idea, mainly black for contrast with the Sakura petals on the attacks, maybe a few pink decals
Attacks can produce sakura petals on Auto, Q and E. Tornado Q can be pink with petals in the tornado:
His recall he can sit down and poor sake into a traditional red dish whilst sakura petals flow around him?
If anyone has any other ideas feel free to add them to it :) The skin would draw heavy influence from 2 Characters from Bleach; kyoraku shunsui and Byakuya Kuchiki plus influence from Japanese culture.