As we don't know what they worshipped it's hard to say what the stones represent. They could have been war trophies. They could have been family totems from a tribe that moved. They could have been a wedding present from a Preselli based chief on the marriage of his daughter to a Salisbury chief's son - Stonehenge having been built purely as a place to hold a significant wedding which put an end to generations of war between the two groups.
Any theory is a valid one unless it involves reptiles.