One aspect of Southern Gothic is defined by attention to the macabre, and Emily in "A Rose for Emily" certainly would fulfill this aspect of the literary tradition. The obvious point to prove it is her keeping Homer's dead body in the upstairs room for close to forty years, but it is the more subtle macabre details of the story that really enhance this story's belonging in this tradition.
Consider the following:
1. the long hair on the pillow, suggesting that she was sleeping with the dead body of Homer for several years after his death.
2. Her unwillingness to let the town bury her dead father -- indicating an inability to accept change and also showing a lack of typical reaction to a dead body.
3. The decay of her home, and its being eyesore even surrounded by buildings that are eyesores.
4. The dust and disuse of her home as mentioned in section 1 and 5 of the story.
5. The Negro man whose voice has "grown dusty with disuse."
6. The mysterious smell around her house that the townspeople came to spread lime for (we realize later was Homer's dead body.)
7. The demand for arsenic -- clearly a poison that will be used to kill someone.
All of these details suggest a "grossness" surrounding Miss Emily. These macabre details create an atmosphere of death and decay that prevades the entire story and builds to the climatic and most macabre detail in the final line of the story.