If what you've done is just edit it into your own creation, I suppose it is legal. When it comes to art, artists "steal" from other artists in the way of taking aspects of their art and morphing it into their own, along with adding a little bit of their own style. However, if you're just going to put little edits on an already existing work... it may not be illegal, but that isn't particularly original, nor what art's all about.