You can go the metaphorical route and photograph a person "feeling" alone or abandoned, or perhaps a physical object, something that people tend to leave behind (cigarette butt, a forgotten plant, sports equipment gathering dust in a corner). You can photograph an object such as this inside of an abandoned building which would really drive this emotion home. Of course an abandoned building would be an ideal canvas for a challenge of this kind, just make sure you are keeping safe and obeying your local laws!
Post your photos here when you have them. We look forward to viewing your works of art.