More imagery than symbolism can be found in Antigone, but there is some of both.
Imagery refers to any words that form a mental picture in the readers' heads. It especially refers to sensory language that can be used to describe "actions, persons, objects, and ideas" ("Guide to Literary Terms," eNotes). We especially see imagery being used when describing death in Antigone. For example, Antigone paints a very vivid description of her brother's corpse being dishonored when she describes it as a "sweet find for birds to feast upon" (30). The reference to the birds feasting is a sensory image referring to taste that conjures up a vivid image of the deceased being mangled by hungry birds. We also see Ismene using imagery when she describes their parents' deaths, especially in the lines describing their father "smiting both his eyes with his very own hands" (52-53). The reference to the senses of sight and touch helps us to see the pain that Oedipus caused himself by scratching out his eyes.
Symbolism is any words, places, or objects that an author uses to convey meaning beyond what is literally meant. One instance of symbolism is seen in the reference to stone. Creon has decreed that anyone who buries Polynices will be stoned to death; also, Antigone is sentenced to be buried alive in a stone cave used as a tomb. Stone has historically been understood to symbolize strength, stability, endurance ("The Symbolism of Stone"). Therefore it is ironic that stone is being used so often in reference to Antigone's family. Antigone's family is anything but strong, stable, and enduring. Instead, they have been cursed by the gods and are all dying. Therefore, in this story, stone is being used to ironically symbolize the family's weakness and close ties to death.
Another instance of symbolism can be seen in reference to burial. Proper burial symbolizes honor and respect. But, again, ironically, Antigone's family is anything but honored and respected. Therefore, again, burial not only symbolizes the family's ties to death but also symbolizes how they have been cursed and dishonored by fate and the gods.