This graveyard scene seems presaged by the words of Hamlet to Claudius in Act IV:
Your fat king and your lean beggar is but variable service--two dishes, but to one table. That's the end....a king may go a progress through the guts of a beggar. (IV,iii,22-29)
In Act V of "Hamlet," gravediggers jest about the various skulls that they dig up; all are equal in death. Even Ophelia whose political status allows her to be buried in the cemetery when she has committed suicide will be equal to the lowly beggar. The skulls of all the dead are equal; they might belong to any person. So, they symbolize the dead person stripped of all status from life.
That a clown and others jest seems inappropriate to the scene. The gravediggers make grim jokes about the deceased and one man drinks a tankard of beer. The men have become callous in their job or repeatedly dealing with dead people. Furthermore,the sanctity of death is parodied as one man sings of love--
O, a pit of clay for to be made/ For such a guest is meet--and the brevity of life.
All men and women end up in the same state, dead.
The motif of death and birth is present in the Clown's remarks that he has been digging graves since the day of Hamlet's birth. Yorik the juggler's skull, which has been part of the jests, also serves to represent the age/youth motif since the young Hamlet sat on his knee. The clown's mention of King Hamlet having defeated old Fortinbras of Norway on young Hamlet's birth day, affords Hamlet some respect with this allusion to his royal birth.
When the King, Queen, and others appear, the Queen strews flowers upon the grave of Ophelia, who is forbidden the full rites of burial. These flowers, then, may symbol the loss of this innocent young woman whose loss is tragically felt by her brother Laertes who jumps into her grave, begging to be buried with her.