Final answer:
The principle of design that features a large difference between or opposing elements in an artwork is 'contrast'. Contrast is used to create visual interest and highlight parts of the artwork, establishing a focal point.
Step-by-step explanation:
The principle of design that features a large difference between or opposing elements in an artwork, such as rough/smooth textures, light/dark values, or geometric/organic shapes, is contrast. Contrast is used by artists to create visual interest and draw attention to certain parts of the artwork. For example, contrasting colors like black and white can bring vitality to a piece or provide subtlety with monochromatic colors, contributing to the unity and variety in the final artwork. The power of contrast can also be seen in how it supports the focal point, like when an artist places a string of gold in a field of dark purple, causing the gold to pop out and become the center of attention.