You're calling this a "writing exercise," prompted by a photograph. Okay. Mission accomplished. Now, forget the prompt and figure out what needs to be done to turn this "exercise" into a story that a reader will come away from with a sense that it was a journey worth the effort.

Right now, it's not a story. Your main character does nothing, figuratively and literally. The action, such as it is, takes place in a dream world that feels like a rough sketch Christopher Nolan might have come up with as he was forming his ideas for "Inception." It's certainly no crime to borrow ideas. The fatal flaw, whether with borrowed material or original concepts, comes when you present your set up as though it were the actual story. Setups are not stories, they are the conditions out of which stories might take shape. That has not yet happened here, but it could. I would suggest that a place to begin is to exploit the tension between the real world, and the dream world. "Inception" blurred the boundaries to the point that not even the audience was sure which was which. You wouldn't need to go in that direction. There's much potential in a character who finds himself unwillingly tossed back into reality after a 17 year sleep, trying to cope with loss in both his real life, and the longing to return to the dream world. Whichever way he turns, he must give up something. Which means a decision. Bingo. That's when you have the reader thinking, "Gosh, I wonder he's going to do."

However you approach it, you need to make this story about the character himself, not just the conditions surrounding him. Compelling chacters need options; they have to make decisions, take actions and then deal with the consequences. If those consequences are unexpected, well, then more decisions and more actions might be required. An action here, a decision there, pretty soon your talking a real plot. And, as we watch him work through his situation, we'll begin to get a sense of who he is, which sounds suspiciously like character development.

Make us wonder what's going to happen next. This implies, of course, that there is a next. For that to be the case, there also needs to be something happening now, in order that our curiosity might be triggered. But that's what will keep the reader reading. And that, of course, is your only real requirement.