We’ve seen it before. The wrong earrings can have a dramatic effect on the look of your face. For instance (as this video mentions) long earrings (the type that almost touch the shoulder) can have an elongating effect on face–good for a round face but certainly not so good for a longer face.
The easiest way to tell? Grab a selection of earrings, pull your hair back and stand in front of a good, well-lit mirror. Then try each pair, one by one. When you try earrings on sequentially like this, its much easier to tell whether a pair is a right fit for your size face.