Two kinds of board
Vision board (Context → Vision board): the artist's overall look across everything.
Release mood board (open a release → Creative, at the bottom): the look of one release, which can differ from the artist's usual style.
What to add
Covers you love, photos with the right energy, colors and textures, fashion, places, film stills. Anything that looks the way the music feels.
Analyze
Add your images, then run the analysis. Apollo reads the colors, mood and themes and uses them when it suggests artwork, posts and rollout ideas. When the direction changes, add or remove images and analyze again. The new analysis replaces the old one.
Tip
A dark, moody artist can still put out a bright summer single. Give that release its own mood board, and Apollo will suggest visuals for that release from it.