The pilot was landing the tail-wheel equipped airplane in variable wind conditions, and subsequently touched down with a quartering tailwind. The airplane veered off the runway to the right, ground-looped, and came to rest back on the runway. During the excursion, the airplane impacted a runway sign. The airplane sustained substantial damage to the right wing during the ground-loop. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.