https://help.cgtrader.com/en/articles/2402234-member-s-rights-obligations-and-representations
The "general" principal is:
"...the Seller represents and warrants that:
the Product is his original work, and contains no copyrighted material of any kind that Seller is not the exclusive owner of..."
In your case you should address this question to the CGT Team (support@cgtrader.com), providing the details that are specific to your intentions and wait for the answer before you do anything.