Symbolism, Imagery, Allegory
Stone Cold
As Bob Dylan once sang, "everybody must get stoned."
There's a reason that Jackson landed on death-by-stoning: a crowd-generated death. In other words, stones allow everyone in the village to participate freely (and excitedly) in the ritual, from the youngest children to Old Man Warner. The horror of "The Lottery" isn't just that someone is murdered, or even that someone is murdered and everyone watches—it's that everyone takes part in the murder.
As the narrator of "The Lottery" observes, "[the villagers] still [remember] to use the stones" (76).
Stones are also significant as murder weapons because the first human tools were made of stone; this lottery really does seem to have its roots in the earliest type of violent human ritual.
What's more, stoning comes up specifically in the religious texts of all three of the Abrahamic religions: Christianity, Judaism, and Islam. Stoning has a strong religious association with community punishment of abomination; in other words, stoning is the classic means for expelling an outsider to reinforce group beliefs.
Good choice there, Ms. Jackson. Death via trapdoor and shark tank just wouldn't have been as resonant.