what characteristics make Egyptian art distinct and unique?
There are many distinctive characteristics of Egyptian art. These include:
Pigment Choice: color choice was symbolic for ancient Egyptian art. Six pigments were used, each with its own meaning:
red - power, life, victory
green - new life, growth, fertility
blue - creation
yellow - eternity (sun or gold)
white - purity, sacred items
black - death, the underworld and the night
Symbolic Elements and Hierarchy: artists were ranked by their implementation of laws that strictly governed the elements of art works.
Scale, for example demonstrated the hierarchy. Kings and Gods were represented by, relatively, large characters (both graphical and in text).
Registers also conveyed hierarchy. Scenes were divided into vertically sorted registers. The higher the register, the more important the content.
Regularity and Simple Geometric Form: across all media (most notably engraving, sculpture and painting), Egyptian art has similar form and structure. These forms persisted over several millennia.
Art works were not used for self-expression, but rather to convey events, or accompany the deceased through the afterlife. Most artworks, especially those in tombs, was not meant to be 'displayed' in the way that modern art is.
These rules are discussed further at: fhttp://mheducation.co.jp/data/QuestRW/sp/2.pdf - it's a worksheet, but the second and third 'summary' pages should help.