From an interview with W.J.T. Mitchell about how to understand what is meant by visual culture, which I tacitly understand as the world of images we live within. Mitchell says:

The concept of visual culture as a discipline or field is quite comparable to linguistics. Linguistics is the general science of language, of all languages; more narrowly, linguistics is the science that deals with the structures of language that underlie any particular speech act or textual formation. The aims of visual culture as a discipline are somewhat analogous. It has the same relation to works of visual art, as linguistics has to literature; visual art is to literature, painting to poetry (a very traditional comparison) as visual culture is to language in general. What visual culture – the visual process of seeing the world as well as making visual representation – “lacks,” then, is a structural, scientific, systematic methodology. There is no Chomsky or Saussure for visual culture (unless you think of Panofsky and the Warburg school as aiming in this direction, toward a “bildwissenschaft,” a science of images). And this lack of a scientific theory of visual culture may be the result of a fundamental difference between visual perception, imaging and picturing on the one hand, and linguistic expression on the other.Language is based on a system (syntax, grammar, phonology) that can be scientifically described; pictures and visual experience may not have a grammar in this sense.

Mitchell goes to say that just as the study of literature forms a subset of the study of language, so visual art is just
one area of visual culture. He adds:

Art history – at least in its traditional formations (and this is changing today) – is not enough by itself for the study of visual culture because is grounded in a distinction between (for instance) mass media, mass culture, kitsch, commercial art and “fine art” proper. Art history is not concerned with ordinary everyday practices of seeing, what I call “vernacular visuality,” all the social constructions of the visual field that lie outside image-making, and artistic
image-making. Before people make images, much less works of art, they look at each other and look at the world.