Which of the following is not an ELEMENT of design?
a. color
b. line
c. emphasis
d. texture

Which of the following principles of design describes the aesthetics and flow of the design?
a. Rhythm
b. Proportion
c. Balance
d. Color

relief sculpture - images are set against a flat background.

a coin is a good example: the inscription, the date, and the figure are slightly raised above a flat surface. the ancient egyptians sometimes carved figures into a flat surface.  

pro: they take significantly less time to make and do not require as much tools or skills as free-standing

cons: not nearly as realistic, as it is not fully 3-d, and does not have the details that a free-standing one does.

freestanding sculptures (also called  carved in the round) are not attached to any  background.   they are 3-dimensional  and fully rendered.