The Darkmoon Storage Box is simply a 14-slot bag, which won't impress anyone with the Tailoring skill or a character level past 60, but is invaluable to a lower-level player.

Source: https://gamerant.com/world-of-warcraft-classic-best-darkmoone-faire-prizes/

Whitemane’s iconic hat and Herod’s shoulder armor are two notable examples, but players can also buy special Scarlet Crusade ensembles from the Darkmoon Faire if they collect the Tabard of the Scarlet Crusade from the Scarlet Halls dungeon.

Source: https://gamerant.com/world-of-warcraft-dragonflight-trading-post-scarlet-crusade-cosmetics/