The blank paper symbolizes saftey, security, life, and good luck.
"The flowers are blooming profusely and the grass was richly green."
The stones symbolize death because they were used as a way to slowly and painfully kill townspeople in a barbaric way.
juxtiposition for extra credit
Old Man Warner said that the other towns that were quiting the lottery are a "pack of crazy fools", yet he and his townspeople barbarically kill a random townsperson every year that they know very well.
pack of crazy fools
I think a possible theme for this story is how society can normalize anything. The townspeople become accustomed to the idea of murdering innocent people because they grew up in an environment where this is normal.
There is a juxtaposition of peace and violence. In the beginning of the story the people seemed like your normal everyday small town citizens, but at the end of the story you see a totally contrasting violent behavior in them.