The paintings are contemporary arts and they are illustrations of Hong Lou Meng ,a chinese novel created in Qing dynasty.
For the author didnt specify the dynasty the story set in,there are many opinions and not a conclusion.Many people think the story is set in Ming dynasty but many think in Qing dynasty.
As to the illustration, it depends on whats the painter's opinion to the story.
It seemed that the painter think the story is set in Ming dynasty or maybe the painter deliberately shift off the argument cause the dresses are not very typical.