I would first suggest that you choose a story (or specific topic) that you know and have read or studied previously, or at least one whose subject matter interests you. Once you have narrowed down your choices, try determining a specific theme or conflict within a story that might serve as a topic for your essay. Hopefully one of them will spur your interest further, and you can go on from there. I won't offer any specific themes or titles, since I really believe you should select one in which you are already somewhat knowledgeable or familiar. In the thesis, you should take a direct stance (pro/con, positive/negative, compare/contrast) about your selected topic.