In many cases the second layer, too, doesn't describe specific content, nor does it provide a context that might give the viewer at least a clue as to what's what. It can be disheartening to have laid down a couple of layers on your page and still not have much narrative content to show for the effort. Don't give up, though. Chances are your image is one where the shapes don't get their identity until the darks go down.
With a little practice you will get in the habit of asking when the shapes become recognizable before you begin to paint. If you can see that the darks will do the work of bringing out the meaning of your strokes and washes, this is very good news. It means that you can be casual in the early stages of the painting, giving the paint room to flow.
The following images are part of a new crop of photos, including some in which the final layer can be counted on to pull the whole painting together. To identify these, imagine what they would look like if you painted only the darkest darks. For homework, please choose one or two that you think will work and paint the pattern of strong darks by itself, just black shapes on white paper. Stand back and see if, in fact, the darks tell the story. If so, dry the study thoroughly and, in a carefree manner block in the middle values and the lights right on top of the darks.
Most likely, what you will see is that this is an image where what is usually done first could be done very loosely.
It might be a good idea to read this again before you start your homework. It asks you to work backwards.