Knowing Imagination

One of the best examples of the use of the imagination is visionary art. According to Wikipedia: Visionary art is art that purports to transcend the physical world and portray a wider vision of awareness including spiritual or mystical themes, or is based in such experiences. Some famous artists of the past that fit this description are Hieronymous Bosch, William Blake, Gustave Moreau, and Ernst Fuchs.
One contemporary artist who is considered to be visionary, and a favorite of mine, is Alex Grey, whose work is truly mind-expanding and illustrative of experiences and conditions difficult to otherwise describe. In his book The Mission of Art (1998) he states that artistic creation can and should contribute to the enlightenment of the artist and the viewer of the art production.
Some of the many additional additional resources are The Society for Art of the Imagination; American Visionary Art Museum in Baltimore, MD;  Visionary Review; and Raw Vision Magazine.