Balance refers to the feeling of Stability or balance of a work of art. Now, There are three types of balances: symmetrical, asymmetrical and radial.
Symmetrical balance is easy to see. It is when two halves of a work are identical or very similar. This can be top and bottom, side to side, or any other direction you want to split the Piece down the middle.
In this case, symmetrical balance is provided by the mirror opposites of Color, not shape
Asymmetrical balance takes into account of qualities such as hue, intensity, value, size and shape. The qualities have an effect on the 'weight' of objects in a work of art. You must take into consideration that Qualities like those listed will affect how much "weight" is in one area of the piece.
This Piece is also Asymmetrical as the difference in shapes are offset with the weight of the heavier color.
Refers to balance within a circular shape or object.
Emphasis is also known as contrast. It is a way of using the elements to stress the difference of certain elements. Emphasis would be accomplished by using sudden and abrupt changes in elements.
Usually, emphasis is used to direct and focus the viewer's attention to the most important or centers of interests of a design. Centers of interests of a design are areas of a piece where you look at the most and hold your attention, because it catches your interest.
Harmony refers to a way of combining similar elements (line, shapes, color etc.) in an artwork to accent their similarities. It could be accomplished by using repetition and gradual changes. Pieces that are in harmony have an overall uniform appearance.
Variety is a way of combining elements in ways to create complicated relationships. A picture may have a variety of hues, values, lines, textures and shapes.
A picture made up of many different hues, values, lines, textures, and shapes would be described as complex. Complex pictures increase visual interests. However, keep in mind that harmony and variety are not opposites. A careful blend of the two principals is essential to the success of almost any work of art. Artist who only focus on harmony and ignores variety might find it easier to achieve balance and unity. However, visual interest in the piece would be lost. On the other hand, artists who only focus on variety and not harmony would make their works too complex. As a result, the viewer would be lost and confused. Furthermore the overall unity of the piece would be lost
Gradation refers to a way of combining elements by using a series of gradual changes. For example, a gradual change of small shapes to larger shapes, or a gradual change of a dark value to a light value, would be gradation. I wont go into much detail here, as I am sure we all know what Gradients are, just keep in mind that they apply to more than just color.
Movement is used to create the look and feeling of action. It guides and moves the viewer's eye throughout the work of art. Movement is achieved through placement of elements so that the eye follows a certain path, like the curve of a line, the contours of shapes, or the repetition of certain colors, textures, or shapes.
Rhythm is a principle that is closely related to movement. Rhythm is a principle of art that's difficult to summarize in words. Assuming that you've picked up on a rhythm in music before, take what you heard with your ears and try to translate that to something you'd see with your eyes. Rhythm, in art, is a visual beat.
A pattern has rhythm, but not all rhythm is patterned. For example, the colors of a piece can convey rhythm, by making your eyes travel from one component to another. Lines can produce rhythm by implying movement. Forms, too, can cause rhythm by the ways in which they're placed one next to the other.
Really, it's easier to "see" rhythm in just about anything other than the visual arts. Literally-minded types should stick to music for rhythm.
Proportion is used to describe the relationship of certain elements to the whole and to each other. It is a principle of art that describes the size, location or amount of one element compared to another (or to the whole) in a piece. It has a great deal to do with the overall hamrony of an individual piece. Its like making a pie, if you have to much salt, your pie tastes like poo. If your art has to much of one element, your art will look like poo.