I'm the artist of the picture. I won't ask you to take it down, though. First, because most people use copyrighted material on their webcam images xD. Second, because I can't take credit for the animation. Nice job, by the way
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Now you know the artist. Which means lots of good things!
Next time someone asks you, you can say, for instance: "Fortunately, I know the artist, she even has a
blog where she submits all her Tintin fanart"
You can avoid trouble or confusion this way
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As I said to your friend, I'd ask you not to submit any more of my art directly in your galleries, but I think you are conscious of it.