There are a number of examples in this excellent sonnet, and even if we look at the first four lines alone, we can definitely see that there are several excellent examples of imagery that can be identified. See if you can see any examples of imagery in these lines:
No more be grieved at that which thou hast done:
Roses have thorns, and silver fountains mud,
Clouds and eclipses stain both moon and sun,
And loathsome canker lives in sweetest bud.
The way in which "clouds and eclipses" are shown to "stain" both "moon and sun" is an excellent example of imagery, and is actually a metaphor, because clouds and eclipses do not really "stain" the moon and the sun in reality, but just block it from our view temporarily. In the same way, the second line focuses on the fact that even beautiful roses have "thorns" and even "silver fountains" have lots of mud around them. These examples of imagery therefore help reinforce the speaker's argument that even in the presence of great beauty there is always some kind of imperfection. The person that the speaker is addressing, therefore, is certainly no different.
I take it you are talking about Shakespeare's sonnet.
"Roses have thorns, and silver fountains mud"
"Clouds and eclipses stain both moon and sun"