This carving on Darius' Apadana shows his subjects, of assumingly different social classes, all lined up, displaying different wares.
The top section displays men guiding and/or riding donkeys, the second displays people holding what seems like swords and other nondescript wares, and the bottom section highlights similar things as the second section.
This displays the different capabilities of the people of Persia, as well as how they were able to contribute to the economy of the Empire.