The moment you publish it (posting it online or in a public place can be considered publishing) it is a problem. Putting “© Windstone” or “Inspired by Windstone” on the image does not make it legal.
e.g. If someone looked at my painting of a dragon, copied it in a way that makes it recognizable as the same, then published it, I can go after them for it. If they publish it and claim credit, or even worse sell it, then I can collect damages (legally) if I so wished.
Does that help at all?
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