This may (or may not) have been a throw a way comment but I googled it 'cus I don't know what they are.
They are:
Shape and Form
Contrast
Pattern
Texture
Lighting
I'm not up for writing 2000 words, what everyone else said.
It was throwaway, in the sense that I’ve heard variously three, five, seven.... I said five [not the five] because I could guess at six and my teaching brain kicked in [anyone who’s done arts-ish courses at uni will remember the calculation]: 500 for decent intro & conclusion, 5 x 300 word paragraphs for each element. (The math for seven would have done me in : )