Symbolism, Drapery
Drapery is one of the symbols that can define a piece as being clearly mourning, rather than being for sentimental purposes. How so? For starters, a pre-existing photograph is simply a keepsake, however post-mortem, drapery over the photograph or portrait with a black curtain would introduce the sentiment of mourning. It’s really quite simple. Another example may be drapery across an unbroken column. The column is usually broken, symbolising life cut short, however, with the drapery over the top of the column, it masks the strength of the unbroken intent and creates the mourning pall across it. From draping/covering the body upon death, the symbolism of the covering as a curtain closing on the life is simple and rich.
Drapery isn’t a Victorian invention, but rather an ancient one, having strong roots in Hellenistic / Classical Greek art quite notable for mourning are various funerary stele depicting drapery across. However, one shouldn’t consider basic drapery as being a sign of mourning across all art, it is specific to its subject, rather than just being an artistic practice of style and technique. Always judge the drapery across the object or symbol for its purpose, otherwise a charming depiction of someone reclining could turn into something slightly more morbid.