The use of dark imagery is more than simply aesthetics on the Left Hand Path. Dark art or any type of art that disturbs the comfortable is a way to access the darkest and most profound aspects of the psyche and you can use it in your practice whether creating your own art or analyzing and meditating on other's works. You can also create dark art as an expression of a ritualistic idea, as a form of blasphemy or painting as a sigil, there are many ways to invoke and integrate these dark energies. The use of art is endless.