Customizing your volleyball sunglasses will make your appearance more unique and help you easily find your eyewear pair. However, take into account that this is a sports gear, so I won’t recommend using ceramic or plastic figures, flowers or signs, rhinestones or pearls: they will make sunglasses heavier, might produce some discomfort while playing or fall and damage your feet.
The best alternative will be painting the frames with acrylic paint. In this case, don’t forget to use the primer before painting to prevent the paint from chipping or scratching. You can also cover the earpieces with scrapbook paper that you can find in craft stores, or apply glitter.