Graphic designs for t-shirts

Looking for someone to create graphics themed for football world cup in Qatar. Graphics should be related to Croatian football team. Graphics will be printed on t-shirts and sold online. Need to be catchy, cool, unique and appealing, printable on different color t-shirts .Your design should be a 300 dpi PNG. Though the image size should be 15 x 18 inches (the printable area of the product), we recommend a design that fits comfortably within that area rather than taking up all of it. Looking to have 20 designs produced in the next 10-15 days.
https://merch.amazon.com/resource/201849250