Maybe this skin concept isn't that special anymore but it would fit perfectly: Phoenix Anivia!
I mean it's a bird that gets revived with its passive.
Maybe her q could be a fire ball.
Her w would be something like a volcano ( because honestly it wouldn't make any sense if for example Vayne would e an enemy and he would collide with a fire wall he probably would just fly through this irl so a volcano is better ).
Actually i'm not sure what her e should be but yeah i think if riot would make this skin real they would also have a good idea how her e should look like.
Her ult would be a fire storm so nothing really special.
It would be very nice if her passive would be an ash heap and then a then she would be reborn from ash and last but not least when she dies she would just burn and would be dead like in harry potter and the chamber of secrets when dumbledores phoenix died.
I hope riot would make this real but although it's such a simple concept it is really a nice and fitting skin concept.