Hm, the "Yachigusa Matsuba" artist for the "Old painting" example is the author, "Yamaguchi Tsubasa", with the letters rearranged, isn't it? It reminds me of a beach. I mean, it doesn't look like a realistic beach, but those first circular things look like footprints in the sand, even if the pattern isn't anything you'd ever see. The darker spot looks like a wet spot on a textile fabric, which has nothing to do with beaches, but gives a feeling of "wet." The line in the corner feels like a receding wave when you don't trace it. The black spots can be anything - crabs, stones, mussels, shells.