Asking for a striped candy-cane nail in December is kind of like asking for a lollipop after the doctor gives you a shot — something we'd like to think we've outgrown. But with the rise of Instagram, and the correlation between trendy manicures and the number of likes you get on your hand-around-the-mug pic, seasonally-inspired nail art has suddenly gone from childlike and cheesy to subtle and chic.