The pilot of a privately owned and operated business jet reported that his airplane was parked on the ramp, with passengers onboard, with the engines operating, preparing to taxi for takeoff. He said that a driver of a tractor tug was parked on the right side of the airplane, waiting for the airplane to move forward. The pilot said that the ramp employee inadvertently placed the tractor tug into reverse, and backed into the airplane's right wing. The airplane sustained substantial damage to the right wing and right aileron.