Nice studies, the only feedback I can think of (and might be advanced compared to the task) is that your light sources seem to be more like a fuzzy laser beam, where usually you want to consider light sources such as sunlight as a sheet of light and the parts of the model that that sheet hits first will be your brightest spots. (orange circles)
Also something to keep in mind, areas that have other things near them (like cavities or dips in the shape) will make it harder for the light to escape, making those spots slightly darker (brown circles) That effect is usually called ambient occlusion.
These 2 points are probably not the point of the exercise, but it's good to keep them in mind for future. Hope this is useful feedback for you! ^-^