Representing

Balance:  The relationship between elements in a given text.  Balance can be symmetrical (both sides of the visual text appear equal -- mirror image) and asymmetrical (balance is achieved by the placement of various elements).

Rhythm and Repetition: Continuous and similar use of elements throughout a text which results in a fluid movement (rhythm) within the visual.  The viewer's eyes are drawn toward the focal point and around the subsidiary elements of the text without being halted or presented with any unaesthetic images.

Proportion:  The size of elements within a text in relation to one another.  This principle can be used to create emphasis, to give the impression of distance and depth, adding to realism.

Emphasis: The application of the elements of design to make one specific feature stand out as the focal point (most obvious centre of attention) of a text.

Variety:  An admixture of the elements of design at points will augment the use of repetition.  That is, change is a good thing -- too much of the same thing can cause a viewer to get bored.  Changes in the use of a specific element (from curved to straight lines, for example) keeps the viewer's attention through visual stimulation.

Unity:  Achieved through the interconnected relationships held between the various principles of design.  All employed elements ought to be integrated in such a way that there is no disparity of meaning (unless that is the goal, of course).

Colour:  Many people underestimate the importance of this fundamental element... selection of appropriate colours has profound psychological effects on a viewer.  Colour has three main properties: Hue (the name of the colour); Value (lightness -- lighter is a tint/darker is a shade); and Chroma (brightness).  Here is a list of some of the connotative values (depending on context) which can be associated with various colours:

Line:  Lines can be curved, straight, long, short, thick, thin, etc. They communicate a sense of movement and direction which adds to the unity and fluidity of a visual.

Texture:  Texture, while akin to the sense of touch, can be communicated visually.  Consider the background of this page... it gives the sense that if one were to touch it, it would be a little bumpy, perhaps like fine sandpaper.  The brain associates impressions with one another... thus a visual that looks textured, gives an impression associated with that texture.

Shape:  Shape, as we all learned in Kindergarten, is the outline of an object in two dimensions.  The use of shape in a visual can create a feeling of proportion and even emotion, etc.  Rounded shapes like circles and ovals create a soft, relaxing feeling whereas shapes with jagged edges and angles like diamonds, squares, etc. can create a sense of pedantic formality.

Form:  Form is similar to shape but instead of two dimensions, it is represented in 3D.  Form can add to the sense of depth in a visual, lending to the ideas of mass and girth.

Space:  Not only is it important to fill a workspace, sometimes, a lot of emphasis can be created by the use of space.  Blank spaces in magazine advertisements (regardless of colour) are referred to as White Space.  White Space allows an author to create focus and emphasis and to communicate a sense of security to the viewer.

Light and Shadow:  Related to value, this element uses the hue of black and white to communicate depth, feeling, emotion, and a sense of atmosphere in a visual.  One of the key areas of study in art school is the use of this element.