if the design is 'royalty free' you can use it - you could include the source of the design on your label- there are tons of 'copy-right free' designs out there---and geometric shapes are something that would be difficult for someone to (claim) as their own---when copyright restrictions come into play is when you are copying a commercial pattern and trying to claim it as your own.
if using someone elses design you should always contact the designer and ask permission-
but even copyrighted designs can be used without permission if the designer is marketing it for public use-...it would be (against the rules) for you to use it commercially---as in offering the design for sale somewhere.