http://en.wikipedia.org/wiki/Gravestone
"Gravestones may be simple upright slabs with semi-circular, rounded, gabled, pointed-arched, pedimental, square or other shaped tops. During the 18th century, they were often decorated with memento mori (symbolic reminders of death) such as skulls or winged skulls (called "death's heads"), winged cherub heads, heavenly crowns, urns or the picks and shovels of the grave digger. Somewhat unusual were more elaborate allegorical figures, such as Old Father Time, or emblems of trade or status, or even some event from the life of the deceased (particularly how they died). Later in the same century, large tomb chests or smaller coped chests were commonly used by the gentry as a means of commemorating a number of members of the same family. In the 19th century, headstone styles became very diverse, ranging from plain to highly decorated. They might be replaced by more elaborately carved markers, such as crosses or angels. Simple curb surrounds, sometimes filled with glass chippings, were popular during the mid-20th century.
Some form of simple decoration is once more popular. Special emblems on tombstones indicate several familiar themes in the Christian faith. Some examples are:
* Anchor - Steadfast hope
* Arch - Rejoined with partner in Heaven
* Birds - The soul
* Cherub - Divine wisdom or justice
* Column - Noble life
* Broken column - Early death
* Conch shell - Wisdom
* Cross, anchor and Bible - Trials, victory and reward
* Crown - Reward and glory
* Dolphin - Salvation, bearer of souls to Heaven
* Dove - Purity, love and Holy Spirit
* Garland - Victory over death
* Gourds - Deliverance from grief
* Heart - Devotion
* Horseshoe - Protection against evil
* Hourglass - Time and its swift flight
* Ivy - Faithfulness, memory, and undying friendship
* Lamb - Innocence
* Laurel - Victory
* Lily - Purity and resurrection
* Mermaid - Dualism of Christ - fully God, fully man
* Oak - Strength
* Olive branch - Forgiveness, and peace
* Palms - Martyrdom, or victory over death
* Peacock - Eternal life
* Poppy - Eternal sleep
* Rooster - Awakening, courage and vigilance
* Shell - Birth and resurrection
* Six pointed star - The God
* Skeleton - Life's brevity
* Snake in a circle - Everlasting life in Heaven
* Swallow - Motherhood
* Broken sword - Life cut short
* Crossed swords - Life lost in battle
* Torch - Eternal life if upturned, death if extinguished
* Tree trunk - The beauty of life
* Triangle - Truth, equality and the trinity
* Shattered urn - Old age, mourning if draped
* Weeping willow - Mourning, grief
Greek letters might also be used:
* αω (alpha and omega) - The beginning and the end
* χρ (chi rho) - The first letters spelling the name of Christ
* IHS - Stylised version of iota-eta-sigma, a Greek abbreviation of Jesus"
Elaborately carved grave slab at Shebbear (Devon, England) showing a skull sprouting flowering shoots, as a symbol of resurrection