For an example of death imagery, take a look at Act IV, Scene I, when the three witches are casting a spell. They list "finger of birth-strangled babe" as an ingredient in their potion. This image of a dead child emphasizes the dark and sinister nature of the witches' magic. It is also important in creating a dark, disturbing mood as the three women cast their spell.
Next, for an image of darkness, take a look at Act I, Scene IV, when Macbeth hears that Malcolm has been named as Duncan's heir. For Macbeth, this creates an obstacle on his path to becoming king, prompting him to create an image of the stars extinguishing their own brightness:
Stars, hide your fires;
Let not light see my black and deep desires.
Finally, for disease imagery, turn to Act V, Scene III, when Macbeth is talking with the doctor. In this image, Macbeth also personifies Scotland as a diseased person who is in need of a cure. Moreover, he compares the English to a disease which needs immediate treatment:
If thou couldst, doctor, castThe water of my land, find her disease,And purge it to a sound and pristine health...What rhubarb, senna, or what purgative drug,Would scour these English hence?
Macbeth, 1.4: "Stars, hide your fires; / Let not light see my black and deep desires." (Macbeth is ashamed of his greed and treachery.)
Donalbain, 2.3: "Where we are, / There's daggers in men's smiles: the near in blood, / The nearer bloody." (Donalbain is fearful of Macbeth's manner and suspects he is up to no good.)
Macbeth, 2.2.: "Will all great Neptune's ocean wash this blood / Clean from my hand? No, this my hand will rather / The multitudinous seas incarnadine, / Making the green one red." (Macbeth reflects on his murderous deed.)
Macbeth, 3.4: "It will have blood; they say, blood will have blood: / Stones have been known to move and trees to speak; / Augurs and understood relations have / By magot-pies and choughs and rooks brought forth / The secret'st man of blood." (Macbeth anticipating having to pay for his crimes.)
Lady Macbeth, 5.1: "Out, damned spot! out I say!" (Lady Macbeth's guilt makes it appear to her that she can never wash the crime of Duncan's blood off her hands.)
Macbeth: 5.3: "Canst thou not minister to a mind diseased...?" (To the doctor. He feels hopeless in the manifestation of his darkness.)