Short answers, pulled from the story.
Decorative arts are arts or crafts concerned with the design and manufacture of functional, beautiful objects. Most objects for building interiors fall under this category yet architecture itself remains excluded from the group.
The Cross of Lothair was created around the year 1000 as a classic example of sacred arts executed in gold and ivory. During medieval times in Europe prestigious works tended to be crafted from precious metals rather than wall paintings.
Works made from precious metals were liable to be recycled immediately when fashion changed or owners needed extra money. Owners often used these items as repositories of wealth to be melted down during financial hardship while paper-based illuminated manuscripts survived at much higher rates.
The Copyright Act 1911 extended protection to include works of artistic craftsmanship previously excluded from legal safeguards. Until that enactment only works classified as fine art had been protected from unauthorized copying.
Arthur Heygate Mackmurdo organized the Century Guild for craftsmen in 1882 to challenge existing hierarchies. This aesthetic movement emerged in England during the second half of the nineteenth century inspired by writings from Thomas Carlyle and John Ruskin.