A reference does what a paragraph of adjectives cannot: it shows the model the thing. It is the fastest route to a specific look, and the most common cause of confusion when a team supplies four references pulling in different directions.
One reference, one job. Style here, composition there, subject somewhere else, and say which is which, because a model given a mood board will average it, and an averaged mood board is exactly what slop looks like.
QUESTIONS PEOPLE ASK
How many reference images should I use?
One per intention. If you need style, structure and subject controlled at once, use separate conditioning for each rather than stacking references and hoping.