What are some of the elements and principles of art that are used in the portrait?

Balance: The sense of stability achieved through implied weight of an object. There are three different types of balance: symmetrical, asymmetrical, and radial.

Symmetrical balance: When one image is mirrored on the other side to repeat itself

Asymmetrical balance: When different types of elements create a visual balance.

Radial balance:The distribution of elements around a central point in all directions.

Here is an example of asymmetrical balance, showing a bright red apple in one corner balanced by a large area of neutral color on the other side. Together, they work to create balance in the overall composition 

A continuous mark made on a surface by a moving point; it may be flat (pencil line) or three-dimensional (a rod, groove, ridge, etc.) Line may be explicit - a line painted along the edge of the road - or implied by the edge of a shape or form. Lines are used to outline (diagrammatic or contour lines), create shading and show form (structural lines, hatching and cross-hatching), decorate, express emotion, and direct the viewer's eye. Lines can be categorized as horizontal, vertical, diagonal, curved, and zigzag.

Lines can be hard, sharp, straight, geometric; they can be organic, smooth, soft, flowing, loopy, wavy.

Lines can remain a constant thickness (descriptive, analytical, objective, showing little of the action used to create them) or vary in thickness along their length (flowing, calligraphic, lyrical, showing emphasis and something of the gesture used to make them).