Because of the many folds and amount of hijab fabric, if you’re going to use accessories beyond decorative pins, consider going bold. Brooches can also add sparkle while keeping your scarf secure. You can try a necklace with big pendant in front of the hijab so that it is visible. Some people wrap a necklace like a crown on top of their head, which is feminine and attractive.
To learn more about face shapes and jewelry, this article on the best jewelry for rectangular faces can give you ideas that you can learn from regardless of your face shape. For example, if your face is rectangular, long earrings make your face appear longer, and square earrings can be too severe. A good solution is to use round, soft accessories and a short necklace length.
Similarly, borrow the idea of asymmetrical shapes when you drape your hijab. For a rectangular face, consider pulling down the hijab and caping your forehead just above the eyes to reduce the appearance of length. Have fun experimenting with folds, volume and sparkle to show off your beautiful face.