What you need to find is a poem that paints only part of the painting, so to speak. Then you can feel free to take the prompt further on your own and describe the scene that you imagine, based on the few beginning words that the poet supplies. I have three recommendations. The text of each poem is provided in a link below.
If you pick Robert Frost’s “The Road Not Taken,” you can follow the first line, “Two roads diverged in a yellow wood.” How do you see these two roads? Are they at all the same? How are they different? Which one would you be inclined to take, if you had to make the choice? What lies at the end of each road?
If you pick William Wordsworth’s “I Wandered Lonely as a Cloud,” you can describe the field of daffodils that he discovers. Take the lines from the second verse, “They stretched in never-ending line / Along the margin of a bay.” How do you see the daffodils in relationship to the water? Are boats sailing nearby? Are any other people walking nearby? Does anyone else see these 10,000 daffodils besides you? Or is this a special place that only you know about? How would it look in summer, fall, or winter, without the flowers?
If you pick Robert Browning’s “My Last Duchess,” you can describe the painted portrait of the woman. Begin with the first two lines, “That’s my last Duchess painted on the wall, / Looking as if she were alive.” Since she was a Duchess, she was part of royalty. What country is she from? What is she wearing in the portrait? What color is her hair? Is she smiling or frowning? Is she holding anything important? Where is this painting hung? Who sees it on a regular basis?
Ask yourself questions, and let your imagination answer them. Then write down what you see in your mind.