Heather -
There are probably more sellers not using a white background than those using white backgrounds. Just search on furniture, dresses, wedding dresses, outdoor and gardening, lamps and dozens of other categories.
For your category, vintage clothing, I'd say at least half the sellers are using something other than a white background
Most sellers of flat art, use no background at all.
For photos that included a person, environmental shots can look very nice. For small items where you want the detail and colors to pop and don't want distraction. single color, generally, white seems to work best.
This is not just Etsy: Big, successful online and brick & mortar retailers do the same. In Mikimoto's online catalog, even white pearls are shown on a white background. Kate Spade, Tumi, Michael Kors, Patek Philippe and even Tiffany use white, or nearly white backgrounds for product close-ups.