Proof? There has to be an original image associated with what is recolored, which is considered theft in most cases. I see no Charizard version of this picture in the artist's gallery, so this is most definitely not a recolor. Just because it looks like something else but with a different exterior, doesn't mean it's a recolor.
This looks great! Usually when Pokemon fans think of Dragonite they envision the cute, innocent-looking one from the games and anime. I love how this picture turns that idea on its head and makes him a fierce, frightening beast instead. He looks thinner than the original sprite--thinner and hungrier, and therefore ready to hunt for prey--and KILL. Amazing job! :-D