For the most part, in this day and age designers would be hard pressed to come up with an entirely different fabric design that hasn't been done before or close to it. Fabric designs have been out since people started making and wearing clothes, whether it is button placement or a flower. There are only so many types of flowers, lines, circles, colors that there are bound to be close calls. Just because someone made a fabric with yellow roses 1" in size, doesn't mean they have rights over anyone else using yellow roses 1" in size. How many designers use polka dots, just because one designer used them doesn't stop others from using polka dots. And there are only so many colors as well. Even a slight change makes it a completely 'new' design, whether it's thread count, color, size, shape. For instance, how many colors of blue are there, that someone doesn't make a fabric the same solid blue as someone else. I also guess, it would depend on how unique the fabric design is and how many changes, even slight the design is. For that matter, I have no idea how copyrights on fabric works or how long it lasts.
Just like fiction books. Basic ideas and story lines have been used over and over again.