Original illustration can bring a more unique feel to websites and company literature. It is especially relevant now as it has become very easy for people to find pre-designed clip-art and stock imagery - having unique illustration will mark you out from the crowd.
Illustration is often used to show a sequence of actions/steps and so can help engage the viewer with your text and give the reader a much clearer idea of what you are explaining to them.
Chris Miller's illustrations have been used in a variety of different ways for example; as part of a logo, website of brochure, to illustrate magazine articles/ advertorials and adverts, also illustration for books, book covers and greeting cards.