http://www.fleurdelis.com/meanings.htm
Crescent: One who has been honored by the sovereign; hope of greater glory (horns to the chief or pointing up)
Decrescent: same meaning but horns facing right or to the sinister
According to the site http://www.goodluckcreations.com/horseshoecharm.html
a crescent moon resembles a horseshoe, and one pointing down means that it will "shower you with Luck". Legend says, that a Horseshoe 'Pointing up' will "gather your Luck,"
Americans of English and Irish descent prefer to display horseshoes upward; those of German, Austrian, Italian, Spanish, and Balkan descent generally hang them downward. People in some parts of Ireland and Britain believe that horseshoes must be turned upward or "the luck will run out."
Horseshoes were actually used by the Greeks as early as the 4th century B.C. Since horses were believed to be one of the most sacred of animals, their crescent-shaped shoes became symbols of good luck. It has associations with the strength and dependability of the horse, and, in upright position it is also symbolic of the moon. Pointing downwards, it is symbolic of the womb.
To the Greeks it symbolized the crescent moon which was regarded as a symbol of fertility.The modern association is more likely to be linked to a legendary tenth century Saint who trapped the Devil in a Horseshoe and as a result made him promise never to enter a Christian home marked by a Horseshoe hung above the door.
(Hope that gives you some idea)