Using a symbol that is not obvious in the story, how would you make a visual representation of Macbeth? The representation needs to be a visual essay with a thesis.

This is an intriguing question! I think you need to determine whether you are attempting to represent the entire story of Macbeth or simply a salient aspect of the story. If you want to represent the whole thing, consider the arc of the play and how you might describe that arc in one sentence. For instance:

A good man is corrupted by his ambitions. Macbeth's desire to be king leads him to commit a heinous act and then to double-down on his crime, in order to protect his new position.

A good man is corrupted by the promise of power. Macbeth was perfectly happy being Duncan's thane until the Weird Sisters suggested that he could have a better life—in this way, Macbeth is not unlike Eve in the Garden of Eden, with the Weird Sisters functioning in the role of the Serpent, tempting a good person to transgress for the promise of "something more."

A good man destroys his life chasing a mirage. Macbeth does not benefit from his crimes and ruins both his own life and the lives of those around him as he tries to achieve the benefit the Weird Sisters seemed to offer him in their prophecies.
Salient aspects of the play include the unsettling meetings with the Weird Sisters on the moor; the murder of King Duncan, who died in his sleep at the hands of his most loyal thane; the madness of Lady Macbeth, who "sold her soul" to make her husband king and lost her mind paying that price; and the ghost of Banquo at the feast, haunting Macbeth with reminders of his crimes.
You can extract some great symbolism from those aspects. The Weird Sisters, for instance, could be represented by any kind of triptych—for example, three standing stones, three trees, three will-o'-the-wisps. Duncan could be a crown, and Lady Macbeth, a pair of bloodied hands clasping each other. Banquo is Macbeth's guilty conscience, and he appears at the feast not so much as an uninvited guest, but as someone who should be present, and isn't. You could show a place setting with Banquo's name on it, at which no one is sitting.
A great format for the kind of thing you're looking to do is collage, because you can bring in various images and align them however you feel makes most sense: for instance, side-by-side, overlapping, or as a central image surrounded by others. There's tremendous scope for creativity here. Decide what your thesis is—the explanation behind your "visual essay," so that viewers understand what they're looking at—and then decide on your imagery. This sounds like a great assignment, so good luck!