People with a thin face can choose sunglasses easily. Many types of sunglasses on a thin face will make the face look good. Here I will recommend you two styles. One is the round sunglasses. round sunglasses are kind of vintage style which is very popular in 2012. When you wear round sunglasses with a vintage hair-style and dress on the street, I promise you must catch a lot of admiring eyes. Another type I want to recommend is the aviator sunglasses. This kind of sunglasses is also very fashionable. Compared with round sunglasses, aviator sunglasses are more serious and suitable for formal occasion.
Personally, I think you can have a try with lovely sunglasses with square frames and round frames. As the square frame make you look serious and round frame balance the length of your face. Both of the two frames can make you fashion and make your face look perfect. As for the color, you can try pink or wine red. They are very fashionable. I think you not fit with sunglasses with too small or too long square frames, because they will make your face longer in look. And too cold color will lose the core of your face. So, lovely square or round frame and warm color will go well with your face.
I envy that you have a thin face which is beautiful, in my opinion. I think the sunglasses with big round frame may fit you and make you comfortable and cute. In contrast, the small ones may be unsuitable. You do not know which one is yours until you have a try. I hope my opinion will be helpful. Good luck!