Grisaille is a term for painting executed entirely in monochrome, usually in shades of grey or brown, particularly used in decoration to represent objects in relief.
Italian examples may be described as work in grisaglia or chiaroscuro, although this term has other meanings as well. Some grisailles in fact include a slightly wider colour range. The photographic equivalent would be a sepia tone.
Grisaille painting due to its apparent simplicity, will render a scene or a subject more attractive or perhaps curious when it is viewed on a frequent basis as part of a decorative theme.