POD is one of the most competitive ecommerce businesses around. There's lots of people trying to work ethically, and corner a part of the huge market for themselves. There are also "bad faith" sellers, who want to lazily leech off the success of others by copying succesful designs and making no effort to develop the idea further or create something unique in any way.
ShineOn Bad Faith Design Policy in a Nutshell
It's fine to seek out successful campaigns to get inspiration for your own designs and niche. It's not acceptable to just copy a design you saw elsewhere.
Copyright law works against POD sellers in many ways, but we won't. If we feel a seller has directly copied another seller's product design, they'll be subject to listing removal and sanctions detailed here.
Getting Your Own Designs Made
It's real simple to get some designs made that are unique and different enough from others. You can find many budding designers in our Facebook Graphic Design group. If you see a design elsewhere you really like, ask them to create something inspired by it, but distinctive and unique for you. Make sure the final design could not easily be confused at first glance for the original design that inspired it.