Let us remind ourselves that imagery is creating verbal pictures through the use of words that appeal to as many of the senses as possible to try and help us imagine the scene that the author or poet is describing in our heads so we can "see" it. Clearly, the powerful imagination of the speaker of this poem as he envisages his rural retreat and the images of natural beauty that he will enjoy lends itself naturally to great imagery. In particular, one of the distinct aspects of this poem are the sounds that are created as part of the imagery. Consider the second stanza:
And I shall have some peace there, for peace comes dropping slow,
Dropping from the veils of morning to where the cricket sings;
There midnight's all a glimmer, and noon a purple glow,
And evening full of the linnet's wings.
Note the way we have combined images that appeal to our sight, with the description of midnight being "all a glimmer" and noon being "a purple glow," but also we have images that directly appeal to our sense of hearing with the sounds of the crickets and the beating of the linnet's wings. Such imagery that appeals to a variety of senses really helps us to imagine the scene and places us there so we can share in the peace and beauty of this man's rural retreat.