Any imagery or design features used within the creative process (sometimes even specific colours etc) used without the express permission of the creator(s) is deemed as a breach of international copyright laws. ESPECIALLY if appropriated for monetary gain.
This does not mean you can copy something and give it away for free either. Anything that has been created or designed, remains the copyright of the creator. Photographs and images too. Even if found on a Google search!
Even though the chances of being sued by the copyright owners is fairly low, it DOES happen ALL the time. There's just so many copying things out there, not everyone gets caught. However, the ones that do get caught have to pay extortionate fines - life ruining sums in the thousands to hundreds of thousands of dollars! Sometimes millions depending on the scale of things!
The best way to avoid being sued by the copyright owners is to create everything for yourself.