Whilst, this, and the other image found on line, are not strictly Sepia Photographs, the first being an old Postcard of a Goya painting, they carry on the theme of Spain and the Spanish Monarchy. I'm not sure why anyone would want to make a Postcard of the particular subject, but I suppose there is no accounting for taste, or even the lack of it. Also, as can be clearly seen, it does not continue the themes of young and beautiful girls.
For the research on Maria Luisa I thank Wikipedia
Maria Luisa de Parma, was the Queen Consort of Charles IV of Spain whom she married on 4 September 1765. As there was no Queen in Spain at that time, Maria Luisa became the first lady of the court from the beginning. Her husband was the son and heir of the widowed Charles III.
Maria Luisa dominated her husband and was believed to have had many love affairs, but there is no evidence that Maria Luisa had any lovers. She was unpopular during her reign and has also long had a bad reputation in history, mainly because of her alleged love affairs and her support of pro-French policies that eventually weren't good for Spain.
Maria Luisa didn't get along with her daughter-in-law because the princess Maria Antonia, guided by her mother, tried to undermine her power. Maria Antonia died from tuberculosis, an illness she had suffered for several years. According to the memoirs of the Duchess of Abrantes, it was rumoured that she was poisoned by Maria Luisa.
Due to pressure from Napoleon, her husband abdicated in 1808, and together with Maria Luisa spent the rest of his life in exile. When Napoleon's army invaded the country, several pamphlets blamed her for that. Maria Luisa spent some years in France and then in Rome, Italy. Both Maria Luisa and her husband died in Italy in early 1819.