The real and conscious relationship between art, architecture, and design is of long standing. Though mural painting was largely neglected in the mid-20th century, in the past great murals have been the planned focal points of interiors and have in a way determined the architecture. Similarly, sculpture or sculptural forms, as fixed and permanent spects of buildings, can be the most important design features if planned that way by the architect together with the interior designer and artist. Perhaps the best design is one in which there is no visible difference between architecture and interior and in which even the artwork is incorporated as an integral part of the total (see photograph ).

The design relationship of interiors to architecture can be clarified by citing an extreme example: the stage set. A set for a theatrical production is a form of interior design but, unlike all other aspects of interior design, it attempts to create its own world and atmosphere concerned only with the play and not at all related to the world or even reality. The creation of a world of make-believe is precisely the function of a stage, but in real life it is impossible to divorce a particular interior from everything else around it. Sometimes a designer may attempt to create a “theatrical” interior, but the point being made strongly and unequivocally here is that every interior must relate to the architecture and to the nearby environment.

Design relationships of individual works of art (paintings, prints, or sculptures) to interiors are most significant in terms of scale and placement, rather than in terms of subject matter, colour, or style. A very old painting, if it is good, will look well within a contemporary interior; a very modern piece of sculpture can be beautiful within an interior furnished with some beautiful traditional pieces. Any work of art, if successful within itself, is “correct” with any interior if properly placed or selected to work with the total space. Certainly there is no need to match colours of paintings to interiors or to select subject matter in works of art that reflect a particular theme, such as food for dining rooms or hunting scenes for the den.

Interiors as they relate to landscape or cityscape are sometimes misunderstood by architects. A crass but typical example is the ubiquitous picture window in suburban housing tracts. Often the only view from the window is the picture window of the neighbouring house. When the view is a beautiful one, it should be possible to plan the interior with the furniture plan and orientation such that seating arrangements can take advantage of the view and yet work for other functions, such as relation to a fireplace or a conversation group, as well.

In many areas of interior design the field of graphics is taking on increasing importance. In every public or institutional building, signs, directories, and room identifications play an important visual part. Good architectural graphics have been stressed only in recent years, as a result of the increasing size and complexity of structures. Buildings such as airports depend upon clear and handsome graphics to make the spaces work and to make them aesthetically cohesive. A related aspect of graphics is the printed matter that is part of certain interior functions. Interior designers must be concerned with the design of menus, wine lists, napkins, and matchbooks in a well-designed restaurant. Designers dealing with stores or shops are concerned with the graphics of shopping bags, signs, and posters. Often the interior designer is the actual graphic designer, or he works together with the graphic designer, just as the architect works with the interior designer or landscape architect.