What are some examples of where Juliet uses imagery?

There is a great deal of imagery in the speech of Juliet, and in many of the other characters; it's Shakespeare, after all! A fair amount of the imagery central to this play arises from the famous phrase used in the prologue, "star-crossed lovers." This image refers to the idea of fate and romance, the belief that fate can intervene in our lives and affect what happens to us, but also that love is a mystical force that draws power from the universe. "Star-crossed" is sometimes said to refer to astrology, and the lovers' suitability for each other may be affected by their respective star signs, based upon the beliefs in astrology that were widespread un Shakespeare's time; but it also means that the timing of their relationship and difficulty of their family situations means their love is cursed. In keeping with this haunting idea of a star-crossed love affair, stars are a frequent image in the play.

The imagery of stars, the moon and night feature prominently in the words of Juliet, whereas Romeo tends to refer to the sun when he speaks of Juliet, as with "what light through yonder window breaks? It is the east and Juliet is the sun." Day and night function as opposites, and also complementary forces (suggesting Romeo and Juliet are two halves of a whole), but also emphasize the importance of time: the speed with which these two lovers become inseparably bound, and the urgency surrounding their situation, because they are forbidden to see each other due to the family feud.

Juliet chides Romeo not to swear by the moon ("the inconstant moon, that monthly changes in her circled orb"), because it is too changeable and fickle. She uses the imagery of night and stars to speak of Romeo as she awaits him one night in her famous "Gallop apace" monologue: 

Come, civil night,
Thou sober-suited matron, all in black,
And learn me how to lose a winning match,
Played for a pair of stainless maidenhoods.

In this quote, night is a maternal, soothing presence. The night is protective in this time of danger when the lovers are worried about being discovered. Juliet feels that the night is helping keep Romeo safe:

Come, night; come, Romeo; come, thou day in night;
For thou wilt lie upon the wings of night
Whiter than new snow upon a raven's back.

But the light of stars reminds her of Romeo:

Give me my Romeo; and, when he shall die,
Take him and cut him out in little stars,
And he will make the face of heaven so fine
That all the world will be in love with night...