Open Book
In anime, an open book is always the main focus. The way artists draw a slice-of-life student frantically studying for midterms or a fantasy mage unlocking an old grimoire tells a lot about the story. Because it is hard to draw detailed text on a curved page, artists usually make an open book the main focus.
This tag has two huge aesthetic groups. Open books are usually spellbooks or grimoires in fantasy. Consider Black Clover, where grimoires literally reveal a character's power, or isekai and magical girl series with glowing, floating text. These works' open books cast colorful, dramatic shadows on the character's face from below. A classic magical trope creates high-contrast wallpapers with movement.
You could also go quiet and homey. Characters sleep at their desks with books open or sit in sunny libraries with scattered novels, evoking the "dokusho" (reading) vibe. These lofi wallpapers have soft colors, warm afternoon light, and detailed environments. The open book makes the character seem stable and friendly. This tag works for epic magical awakenings and cozy character art.