@InspectorCaracal the main goodies i've seen be extremely useful are annotations (scar x, marking y, always wears necklace with additional closeup of it, etc), and colors off to the side in blocks (easily eyedropperable). so a list like - eyes [block of color], fur [block of color], separate from the drawings. even putting a hex code of the specific colors if you REALLY wanna be fancypants and make life easy on artists later commissioned.
@wigglytuffitout *scribbles down a whole bunch of notes* thank youuu