There is symbolism when the children are gathering the stones in the beggining, to them running to get stones in the end, because it shows their naive side and how unknowing they are of what they are doing is wrong.
A great example of imagery is "He was a round faced jovial man" because the text is able to create an image in your mind as to what the character looks like.
Figures of speech pt.2
When reading "a sudden hush fell on the crowd" you don't take the statement literally, as it is an idiom. A hush didn't actually fall on top of the crowd, the crowd just became quiet.
In the beginning of the story the scenery was described "the morning of June 27th was a clear and sunny, with the fresh warmth of a full summer day: the flowers were blooming profusely and the grass was a richly greener." The tone of the story was quickly set as very calm and peaceful.
The text stated "the feeling of liberty sat uneasily on most of them" which is an idiom, something that again shouldn't be taken seriously, has the word liberty ever just sat on you? Your answer to that question is very likely to be no because a word or feeling cannot sit on you.
Juxtaposition is present from the beginning when the scenery is calm and peaceful then when it switches to violence at the end of the story when Tessie is getting stones thrown at her.