From the Model Mayhem FAQ:
Print: My order is damaged. How do I get a replacement?
Please submit your request through the contact form on Shop Contact. We will only replace orders that were damaged during shipping or printed with errors. Please provide the information below in your replacement request.
2. ModelMayhem # if you have one
3. Order number
4. Email address
5. Phone number
6. Explanation of damage or reason for replacement
We will submit your order for reprinting and have it shipped directly to you. We will also provide you a return merchandise authorization number (RMA) so that you can ship the damaged prints back to us.