I would say that Montresor's coat of arms is a really good symbol to analyze in this story. The coat of arms comes up in conversation between Fortunato and Montresor.
“The Montresors,” I replied, “were a great and numerous family.”
“I forget your arms.”
“A huge human foot d’or, in a field azure; the foot crushes a serpent rampant whose fangs are embedded in the heel.”
“And the motto?”
“Nemo me impune lacessit.”
It's a great little exchange because it carries a lot of meaning. Let's start with the motto. It means "no one attacks me with impunity." That references Montresor's opening statement that he plans to get revenge against Fortunato for the "insults." That fits perfectly with who readers understand Montresor to be; however, the motto is the motto for the Royal Stuart dynasty of Scotland. Montresor is not Scottish, so it quickly becomes clear that Montresor is lying. The image on the coat of arms is symbolic too. Montresor is the foot that is crushing the snake (Fortunato). Readers can assume that Fortunato is the snake that bit Montresor, and Montresor is now crushing his enemy beneath his boot/house.