There is an important distinction between "mixed-media" artworks and "multimedia art". Mixed media tends to refer to a work of visual art that combines various traditionally distinct visual art media. For example, a work on canvas that combines paint, ink, and collage could properly be called a "mixed media" work, but not a work of "multimedia art." The term multimedia art implies a broader scope than mixed media, combining visual art with non-visual elements (such as recorded sound, for example) or with elements of the other arts (such as literature, drama, dance, motion graphics, music, or interactivity).
When creating a painted or photographed work using mixed media it is important to choose the layers carefully and allow enough drying time between the layers to ensure the final work will have structural integrity. If many different media are used it is equally important to choose a sturdy foundation upon which the different layers are imposed.Wikipedia