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I am a professional 3D artist and just to shed light on the grey area here. I'll make it very clear. If I create something artistic, I do not need to include a license one way or another. It is protected by law from it's inception. If someone steals that, however, the burden of proof is upon me to prove that I am the creator of the original. If I place a copyright tag on it with date, this can be impled but not a guarantee that I am the original author. Creation dates in CG files help. The best way (outside of registering with your country's copyright office), however, is to generate a physical copy or photograph of your creation and mail it to yourself in a sealed envelope. The sealed envelop will have a date stamp from the postal service on it. Never open the envelop except if the need should arise in a court of law over a dispute of copyright ownership.
To make it clear, again, a work of art does not need to have any implicit license or copyright tag to be protected by law. It is always protected.
