Imagery is description that appeals to the five senses of taste, touch, sound, sight, and smell.
Several examples of revenge imagery show up in Hamlet's soliloquy about Fortinbras in act 4, scene 4. Hamlet is still trying to force himself to act and kill Claudius in revenge for Claudius's killing of Hamlet's father. Hamlet berates himself for his cowardice and conjures up images of Fortinbras. He knows that Fortinbras is marching an entire army into Denmark to reclaim a piece of land in revenge for Hamlet's father having taken it from Fortinbras's father.
What is interesting about this soliloquy is that, as much as Hamlet is trying to gird himself to revenge, his images show his deep ambivalence about whether vengeance is worth the price. For example, he describes Fortinbras as, like other great men:
find [ing] quarrel in a straw
When honour's at the stake.
What Hamlet is saying is that Fortinbras is fighting over a "straw," something insubstantial, commonplace, and worthless, but doing it for honor—calling into question if this is a good act.
Nevertheless, Hamlet continues to try to compel himself to kill, using bloody imagery to describe his revenge:
O, from this time forth,
My thoughts be bloody, or be nothing worth!
In this play about revenge, Hamlet is not the only one using revenge imagery. Laertes comes back from France hot to kill Hamlet for murdering Polonius. Laertes says to Claudius that he wants to
To cut his [Hamlet's] throat
i' the church.
This conjures up a particularly bloodthirsty set of images and juxtaposes the sacred and profane in a chilling way.
In act 5, scene 2, Hamlet uses images that conjure up in blunt terms ("kill'd" and "whored") what Claudius has done that deserves revenge. He then imagines his own "arm" as an instrument of vengeance:
Does it not, think'st thee, stand me now upon--
He that hath kill'd my king and whored my mother,
Popp'd in between the election and my hopes,
Thrown out his angle for my proper life,
And with such cozenage—is't not perfect conscience,
To quit him with this arm?