Media collage is a subset of collage. Strictly speaking, it's an unnecessary phrase, because all collage inherently works with media, in the broader sense of the term. However, "media collage" generally refers to collage that works with media in the modern, narrow, and somewhat sloppy sense of "photo, sound, and electronic media." Some artists that work with sound and film collage are Negativland, John Oswald, and the Tape-beatles. I think I saw a film collage on RTmark.com.