The images that are evoked in Hughes' poem are largely negative as they are the result of dreams being denied or deferred, put off and not realized. For this reason, I think that one can see how these images evoke a sense of anger and frustration in a setting where people are continually told of "the American Dream." The images illuminated by ideas such as "dry up, fester, stink, crust, and sugar over" are all a part of this. The explosion that happens at the end of the poem also is an image where there is a sense of betrayal evident. These images make clear that the promises and possibilities of America are not being experienced by a group of people. The images in this light are more reflections of this. I think that these go beyond the standard view of "positive" or "negative" images because of their reflection of a state of being for many at the time of writing. Hughes is convinced that there is a segment of the American population that is experiencing a blight in their dreams and a deferral in what it is they wish to pursue. This experience is one that results in a variety of responses, and where the images become a representation of these responses.
Langston Hughes puts ground underneath the idea of dreams, and compares them to very concrete things in our everyday lives. Sure, we personally might not immediately liken dreams to raisins, festering sores, rotting meat, and heavy loads, but through this poem, our speaker wants us to understand the reality of dreaming and the danger of not acting upon our dreams.