Marvel Hero skins

So they came out with a Night Crawler skin for Rengar... Why didnt the come out with any for other champs? I can think of tons of cool ideas like: Ironman Ezreal , Daredevil Lee SIn, Captain America Braum, Groot Maokai, Pyro Brand, Storm Janna. I think that these would be cool to have in game. I dont know if Riot could legally do this, but if so...... MAKE IT HAPPEN