In history the Kushan Dynasty was a Buddhist principality in what is now Afghanistan. The Yu-Chi people, ruled by the Kushan, took over much of south central Asia. From Iran through Afghanistan to Pakistan and Northern India. The first Kushan Yabgu(Prince) was Saban whose reign began in ~30 BC and their reign lasted until about 360 AD. The Kushan are usually pointed to as the group that built the great idols of Buddha in the Afghani mountains that a few years ago were being used as target practice by the now mostly defunct Taliban.
(More information can be obtained from http://www.kushan.org)
In Relic Entertainment's 1999 game of the year, Homeworld, the protagonist race is given the name Kushan. The story goes that the Kushan had once built a powerful empire in the Galactic Core but were ousted from power by the mighty Taidanii, who were forced by the Galactic Council to grant some amnesty to the defeated. So the Kushan were fored into exile, sent on gigantic, poorly made prison transports. But they took with them a piece of their homeworld's sacred angel moon on which a map of the galaxy and a word were etched. The word was Hiigara, it represented to the exiles the chance to return. They are sent to a world called Kharak after generations of wandering, a desert world not entirely unlike Afghanistan.
In the game the ambient music was composed using the instruments and traditional styles that characterize the region today, though how they correspond to genuine Kushan musical tastes is indeterminable.
Ingame the Kushan are characterized by their Kiithid system of government. The Kiithid formed as early as the trip from Hiigara to Kharak on the prison transports and turned into clans formed around common religious, cultural and racial backgrounds.