According to Dragon Robes ( a lovely online exhibit provided by the San Diego Museum of Art), "Fingernail protectors were worn by a very elite group–Manchu court ladies of the late Qing dynasty. Although scholars of Chinese costumes usually date fingernail protectors to the Qing dynasty, they are in fact characteristic only of the late 19th century. Portraits of early Qing court ladies show natural fingernails. Late Qing rulers, however, pursued a life of absolute luxury. For example, photographs and portraits of Empress Jixi (1835-1908) show her wearing two or three nail shields on each of her hands–a sign of her ability to rely upon servants to carry out any of her wishes, as she herself could perform no manual tasks." [Qing Dyansty: 1644-1912]
The wearing of fingernail protectors was specifically associated with the Manchurian high culture of the Qing Dynasty. Han men were forced by law to wear Manchu clothing and to groom themselves by Manchu custom, whereas Han women were free to continue wearing traditional Han fashions. According to the Global Chinese Language and Culture Center, "Manchu women felt that long fingernails were a status symbol they protected them with fingernail covers that were finely carved and inlayed with gold silver and gem" (see site for photograph of gold nail protector).
the fingernail guards pictured here are all from the nineteenth-century, one as early as 1850
the materials used include silver wirework, gold overlay, and tortoiseshell bases with decorative applications of cloisonne enameling and inset gems and semi-precious stoneds including polished turquoise, coral, and pearls
Wooden dolls in China (called royal or merchant dolls) often showed the long fingernails worn by wealthy members of society. This one, displayed on Lotz Doll Pages, is a prince:
Cosmetic enhancements of the nails may have originated in China and Egypt around the same period, around 3000 B.C. Per the Wiki, "The Chinese used a colored lacquer, made from a combination of gum arabic, egg whites, gelatin and beeswax.  Another product used by them consisted of mashed petals of roses, orchids and impatiens combined with alum. (Applying this mixture to nails for a few hours or overnight leaves a color ranging from pink to red.) The Egyptians used stains to color their nails as well as the tips of their fingers. The stain they used was a reddish-brown dye derived from the henna plant...
During the Chou Dynasty of 600 B.C., the colors chosen by Chinese royalty to enhance their nails was gold and silver. In a fifteenth-century Ming manuscript, red and black are said to be the colors royalty had been choosing for centuries as their colors. Among the Egyptians, too, nail color came to signify social order, with shades of red at the top. Queen Nefertiti, wife of the heretic king Ikhnaton, colored her finger and toe nails ruby red and Cleopatra favored a deep rust red. Women of lower rank who colored their nails were permitted only pale hues, and no woman dared to flaunt the color worn by the queen - or king, for Egyptian men, too, sported painted nails."
Fingernails have another, more practical importance in traditional Chinese culture. They figure prominently in medical palmistry, being -- along with the tongue -- a bodily feature used for the diagonsis of disease.
Fingernails also figure in the playing of some traditional orchestral instruments, such as the pipa and the zhongruan, in which "fingernail technique" allows musicians to achieve a greater range of sound.
Even today, fingernails still hold some fascination in modern China and Chinese diasporic culture. Young Chinese men sometimes sport a long finger nail (which is thought to express luck, health, viritility, and/or intelligence if it grows as long as the last knuckle on the ring finger). And, in 2000, when the Indian man (Shridhar Chillal from Pune, near Bombay) who for twenty years has been the Guinness Book of World Records holder for the longest fingernails decided to remove and auction them off, he did so -- where else? -- in Hong Kong (CNN). And, in modern Chinese cinema, hopping corpses (what we tend to call Asian vampires) often sport exceptionally long tongues and fingernails. Per the wiki, "Generally in the movies the hopping corpses are dressed in imperial Qing Dynasty clothes, their arms permanently outstretched due to rigor mortis. Like those depicted in Western movies, they tend to appear with an outrageously long tongue and long fingernails. They can be evaded by holding one's breath, as they track living creatures by detecting their breathing. Their visual depiction as horrific Qing Dynasty officials reflects a common stereotype among the Han Chinese of the foreign Manchu people, who founded the much-despised dynasty, as bloodthirsty creatures with little regard for humanity."