Concerning imagery and symbolism in Shakespeare's Macbeth, one of the images you can use that demonstrate something about Macbeth is the bloody dagger Macbeth sees in Act 2.1.
The bloody dagger is an image and symbol of Macbeth's guilt. He has qualms about killing Duncan, but is ambitious enough to let his wife talk him into it. He wants the crown, but he still feels guilty for what he's about to do.
The darkness so prevalent in the play is also a symbol of Macbeth's darkness. Macbeth is dark and evil, and the darkness reflects this. He asks for his thoughts and desires and deeds to be hidden:
...Stars, hide your fires;
Let not light see my black and deep desires,
The eye wink at the hand; yet let that be
Which the eye fears, when it is done to see. (Act 1.4.51-54)
He wishes for darkness, for the eye not to see what the hand does; yet, he asks for that to be done (Duncan assassinated) which the eye is afraid to look at.
Finally, Banquo's ghost is a symbol of Macbeth's guilt. As the play is written, the ghost is real, or actual, rather than a figment of Macbeth's imagination and guilt. But it still symbolizes Macbeth's guilt, as well as his corruption and evil deeds. As Macbeth himself says, the dead do not seem to stay dead anymore. Neither does Macbeth's guilt; and his murderous deeds do not stay hidden.