For the external designs kindly use your own image, art or design. It is violation of copyright to use or copy or distribute an artistic work which belongs to another person or company. Since you are designer of your own product therefore in case of exact similarity with original work it would be considered violation of the copyright, intellectual property right at your own risk. The company will not be responsible for conflicts on intellectual property rights for using external designs.
The design selected by you is an overview of colors on the website and it may differ once printed physically on the garment.
The return of a sold product would only be possible in case of defects or damage or wrong size.