Sve ste lijepo objasnili.

Mislim da nema nikakvog skrivenog značenja, tj. da je u pitanju slobodni izražaj autora teksta.

Na Internetu nema naznaka da bi mogao postojati neki poseban umjetnički pravac izrezivanja krojeva koji bi se zvao „dark art“.

Nije mi poznat kontekst, ali mi mračna umjetnost ima na neki nacin negativnu konotaciju.

Primarily a product of the 20th Century, dark art is an art style defined as that being "dark" or unsettling in nature. Called and classified under many names such at gothic, horror, metaphysical, nightmarish, and disturbing, it is actually a culmination of techniques and styles. It has been presented in many forms by many artists, illustrators and film-makers. It continues to grow in popularity as a part of the horror genre and gothic, music & publishing culture. Today, it a part of our mainstream culture, crossing over into multiple mediums including advertising, television, film, and marketing. While it has roots in horror, it has been presented in collage, surrealism, abstract, motion graphics, grunge, expressionism, and largely digital art.

Znam da ovo nije odgovor, ali možda pomogne. Ja bih ostavila "dark art".