I think that you could take a variety of approaches with this.  Allow me to make a suggestion.  Find the scene online or on YouTube from the show, "Mad Men," that talks about "nostalgia."  (It's a three minute clip that can be found with a web search of "Mad Men" and "nostalgia" being sought.)  The scene is one in which Don Draper uses pictures to convey the feeling of nostalgia and what it means.  This clip might help you establish some of the basis for a potential idea in a short story.  The story could simply be about nostalgia and the yearning of hurt that is caused by it.  It can be told from a point of view of someone who is examining "the picture" or "the portrait" in the light of nostalgia.  In this, their viewing of the picture can become part of the analysis in which similes, metaphors, and juxtapositions between the experience of the present and that of nostalgic recollections of the past can be introduced and developed.  In seeing pictures as representatives of nostalgia, one can develop a story around this experience, making the story a thematic exploration of what it means to yearn for that which is not there.  As Don Draper puts it, establishing a "sentimental bond" with the object, in this case, "the portrait" or "the picture."  It can help to develop a "deeper bond" that is "potent" with the object, making it "a time machine" that allows the subject of the story and the reader to "ache."  In this, one finds great writing.