Balance

Equilibrium: The pleasant arrangement of elements in a composition.

Equilibrium is what can make or ruin a composition.

Imbalance: A composition without equilibrium.

Unbalanced compositions often create an uneasy feeling in the watcher.

Symmetry: When an object's side is the same as the other side.

The right side of this spider is a reflection of its left side and vice versa.

Rhythm

Kinesthetic Empathy: Process in which the viewer recreates an action and/or sentiment when she/he observes.

(Work in Progress)

Rhythm: Element of design based on the repetition of motifs.

Mere visuals can create such sentiments that can soothe or unease our mood,

Progressive Rhythm: The gradual change of a motif in a regular pattern.

This kind of rhythm builds up until it achieves a climax, or an anti-climax.

Scale and Proportion

Proportion: The size of a specific element compared to another one

This are the proportions of a human male.

Hieratic Scaling: Composition in which the hieratic position of an element determines its size.

You can clearly see that the leader of this gang is the big guy.

Surrealism: Style of art that expresses ideas in a fantastic and irrational way.

This image expresses a shape and form that can't be placed on the real world.

Unity

Harmony: The pleasing balance of elements in a composition.

Harmony is created when everything rests at the right place.

Repetition: Re-using the same element over and over again in a composition.

Multiple image can be a form of repetition

Continuation: A line that continues from one shape to another and allows the eye to flow smoothly throughout the composition.

Trying to follow through the body of this lung dragon is an example  of continuity.

Emphasis and Focal Point

Emphasis by Contrast: Emphasis achieved by changing the color, value or color-intensity of the area meant to be the focal point.

A change of hue, value, or intensity can create emphasis by contrast. 

Emphasis by Isolation: Emphasis created by separating an object from a group to draw more attention to it.

Separating one or some from a group calls our attention. This image shows emphasis by contrast and by isolation.

Emphasis by Placement: When the focal point is located in the center or the near-the-center area of a composition.

Even though it is showing multiple subjects, the one in the center calls our attention more than the others.