If you have an oblong face, you'd better choose wide sunglasses to break up the length of your face and widen your long face. Remember not to choose small sunglasses that accentuate face length. The right sunglasses will enhance your face and add complement to your look. Good luck!
If you have long face, you can try a pair of black small round sunglasses that like John Lennon worn. I believe it will be very cool on you. Aside from black small round sunglasses, a pair of small square sunglasses or black wayfarer sunglasses are also good consideration to flatter your face. Hope this help.