A lamb on a headstone often indicates the grave of an infant due to their innocence and this is especially true if there are no other headstone symbols to be seen. The big giveaway is the age of the deceased marked on the headstone if available.
In many religions, the lamb is also a symbol of sacrifice and therefore in some cases, it could be used for a person who was either innocent in life or that the deceased sacrificed something significant in their life time.
Lamb of God / Agnus Dei
Christianity often refers Christ to a ‘Lamb of God‘.
John 1.29: Behold the Lamb of God, which taketh away the sin of the world
The Agnus Dei (Lamb of God) is often shown with a banner/flag and a cross, but it can also be shown with a shepherds crook or the alpha and omega symbols.
Ram’s Head on a Headstone
The ram has long been a symbol of determination, action, initiative and leadership in many ancient societies. Although quite rare, a ram’s head is very popular with witchcraft and may denote the deceased studied it. It can also symbolise sacrifice and that possibly the deceased was an Aries.
When trying to decipher the true meaning of a headstone, you have to look at all of the symbols available.