Some of the brush strokes made me think of river, while the blue stains made me think of sky. The silhouetted characters seemed a bit lost, and tired, the one lying down as though to sleep. In all it made me think of the myth of the River Lethe, the river of forgetfulness.
But what's the horse got to do with it? Perhaps it is memory galloping away? Your interpretation is as good as mine--let me know if you have any ideas, lol.