There are too many items that are potentially symbolic in this short story to really discuss them all in detail. Instead, let's focus on the most important symbols. The first comes in the title. The evening sun is setting. It symbolizes the end of an era—literally a day, but figuratively the time period that produced this situation. (Look at the changes mentioned in the first paragraph for examples.)
Next, consider Nancy's profession. It too is literal; many Black women did domestic labor. However, it is also symbolic: the Black women had to deal with their society's "dirty laundry."
Next, the scar. It too is literal—damage done to the body. However, it also symbolizes how life marks and disfigures African-Americans in this period. Some scars are visible; some are not.
Well there are some symbols in the story, but I think mainly the people are symbols representative of the time. Think of Mr. Stovell who presents as both the economic system (he is a cashier at the bank) and the religious institutions (he is a Baptist deacon) of the South, refuses to pay Nancy for her services. Stovell is representative of all the bad in the South, and how the White take advantage of the Blacks, and don't get punished for it. He represents both the wealthy and the religious.
Another symbol is certainly the way that Faulkner uses darkness and lightness in the story. For Nancy "that evening sun'' represents the danger that her absent lover presents to her. Jesus—whose name is likely an ironic joke on Faulkner's part— represents danger and violence to Nancy, and he will wait until night has fallen to fall upon her. When it is light she feels safer, but once the darkness hits, danger is represented.
One symbol could be the main character who,as presented, symbolizes the maltreatment of whites towards the blacks and the conflict between the two.Another symbol are the children who are not capable of understanding the adult world.Their simplicity and ignorance distinguished their fear of the dark from that of Nancy's.