Final answer:
The design element that includes surface qualities like rust, velvet, or sandpaper is texture. Texture can be tactile or visual and is integral in creating depth and realism in art.
Step-by-step explanation:
The element of design that involves surface qualities such as rust, velvet, or sandpaper is texture. Texture refers to the tactile and visual qualities of a surface, which can range from rough to smooth. It can be both felt with the touch and perceived by the eye. In the arts, texture is utilized to give depth and realism to works, and it is an important component in the representation of various materials like rock, wood, stone, and fabric. Artists enhance their creations by adding texture through brushwork, layers of paint, and the materials used, whether in two-dimensional or three-dimensional art forms.