Like most images on tumblr, it is not mine. I am not the artist. You would need to track them down and ask their permission. If you can’t find the artist, here is my general rule. Will you in any way make money from using this image? If yes, you must pay the artist. If no, run with it, but make sure to credit the artist. I am probably not as consistent as I should be making sure artists get credit. For that, I apologize.