Symbolism, Imagery, Allegory
Eilis' decision to hold on to a photo of her and Jim Farrell shows that she accepts this brief, bizarre period in her life—for better or worse.
The photograph was taken during one of Eilis' beachside jaunts with Jim, and it depicts the couple acting very touch-feely with one another. Eilis doesn't quite know what to do with it when she starts packing up her bags (it's damning evidence of a clandestine relationship, after all), but she eventually decides to keep it, saying that "some time in the future [...] she would look at them and remember what would soon, she knew now, seem like a strange, hazy dream to her" (4.366)
This, of course, is compounded by the ambiguity of the ending, which leaves us questioning what will come next for Eilis' romantic life. By holding on to this photograph of her and Jim, Eilis is saying that her romance with him was real, whether or not she ends up with him, Tony, or some other hunky fellow we haven't even met yet.