Consider the Lilies

Lilies are well-known and are often considered some of the most beautiful flowers. As pure white flowers, they've often been associated with purity, innocence, and virtue. Also, due to their frequent use  in funerals, they've also been associated with death, sympathy, and sometimes even restored innocence upon passing on to the next life. In Ancient Greek mythology, it was believed that lilies sprouted from the milk of Hera, so the Greeks revered the lily and its connection to the queen of the gods. The lily is also associated with Easter, and therefore it could be implied that the lily symbolizes resurrection, rebirth, and hope, though it is usually said to symbolize chastity and virtue.

A little chapel to the Virgin Mary in Notre Dame in Paris, France.

Since the lily symbolizes virtue and purity, it is the symbol Mary, the Mother of Christ, who is the epitome of purity and is revered by Catholics. In most paintings of the annunciation, lilies are almost always depicted in some way. 

Lilies decorating the window grating on the outside of the Musee d'Orsay, Paris. These don't symbolize  anything in particular, but are beautiful and very impressionistic (the Musee d'Orsay is well-known for its Impressionism collection). Claude Monet particularly loved painting the waterlilies in his garden.

 Feur-de-lis decorating the Church of St. Louis of the French in Rome, Italy.

Countless heraldries have used the stylized lily, the fleur-de-lis in French. The most common heraldry that used it were the French kings, and it is even still, particularly with blue and gold colors, a symbol of France. Many people, upon seeing it, call it the Boy Scout symbol, but it was simply adopted by the Boy Scouts and its history goes much farther back through centuries of nations, monarchies, and wars. As wikipedia claims, French historian, Georges Duby, states that "the three petals represent the medieval social classes: those who worked, those who fought, and those who prayed." On this site, it describes the flour-de-lis as symbolizing divine right: the right of kings to rule instead of others, and sometimes even certain kings as opposed to other kings (for example, the English kings claimed divine right to rule over France during the Hundred Years War).

 A painting in the Louvre of Joan of Arc at King Charles's coronation at Reims, France.

 Detail of the flour-de-lis and an inscription.

 A portrait of Marie de Medici, from Florence, Italy, who married the king of France.

Though most prominently associated with France, as I mentioned, the flour-de-lis was used on other heraldries. According to wikipedia and this site, the fleur-de-lis was sometimes used in England to denote or to distinguish a sixth son in his coat of arms (in order to avoid confusion...how embarrassing it would be for someone to think you're the eldest when you're actually the sixth).

Another heraldry that can frequently be identified with a stylized lily, usually red, is the crest of Firenze/Florence, Italy, the golden monarch of the Renaissance until it moved to Rome. It is important to note, however, that the fleur-de-lis is slightly different than the French icon in that the stamens protrude in between the petals. Interestingly enough, Marie de Medici, from Firenze, married the king of France who also used the same symbol as the one that she grew up with in her home city. I found that rather fascinating.