I think there are two elements of imagery that you could point towards Hamlet's character development. First, you have "Something is rotten in the state of Denmark" argument. In the examples below, there is imagery of rotting nature that illustrate that his own heart is being torn out. Secondly, you have the fact that he can't speak about the problems he has found and that he can't act.  I've included samples from each of four soliloquies below:

HAMLET I.ii 

Fie on't! ah fie! 'tis an unweeded garden,
That grows to seed; things rank and gross in nature
Possess it merely.

But break, my heart; for I must hold my tongue.

HAMLET II.ii (1628)

Yet I,
A dull and muddy-mettled rascal, peak,
Like John-a-dreams, unpregnant of my cause,
And can say nothing; no, not for a king,
Upon whose property and most dear life
A damn'd defeat was made. Am I a coward?

HAMLET III.i (1631)

who would fardels bear,
To grunt and sweat under a weary life,
But that the dread of something after death,
The undiscover'd country from whose bourn
No traveller returns, puzzles the will
And makes us rather bear those ills we have
Than fly to others that we know not of?
Thus conscience doth make cowards of us all;

HAMLET IV.iv (1656)

Why yet I live to say 'This thing's to do;'
Sith I have cause and will and strength and means
To do't. Examples gross as earth exhort me: