Don't be bashful! If you want comments, give comments. You don't need to be an expert photographer to express your opinion about the work of others. You don't need to go into great depth. A simple remark about cropping, composition, color, subject matter, etc. can be of just as much help to a budding photographer as an in-depth critique.
The S-curve is a very graceful way to organize a composition. In fact, whenever I see an S-curve in a scene, I try to photograph it. Your assignment is to photograph an outdoor scene in which an S-curve is the dominant compositional element. It could be the water rushing up to the sand at the beach, a road, or trees along a mountain ridge. First, walk the perimeter of what you want to shoot, looking for the best angles and composition. Next, pick up your camera and shoot away. Photograph the scene in a number of different ways, both vertical and horizontal, symmetrical and asymmetrical, using different lenses and different formats.