I spent this past Saturday visiting resale stores, antique shops and thrift stores in my area. While I didn't find any great treasures I did see a few wedding related items.
At the craft/antique mall at I-75 and Mt. Morris Rd there were two different vintage wedding gowns. One was short, like a sheath dress. I didn't get a real good look at it but I'm estimating it was any time from the 20's to the 50's. Another one was long and lacy with the high neck lace collar, Victorian style though I don't know if it was authentic Victorian or Vintage 70's when the high neck styles were back in for awhile.
I also spyed several tiaras, veils and headpieces, some gorgeous vintage jewelry, a couple old cake toppers and some other stuff that could be used in a vintage theme wedding.
The antique mall, R&J Needful Things, on Pierson Rd in Flushing didn't have much wedding stuff but they had plenty of cool antiques and vintage items that could easily be incorporated into a vintage wedding.
If you would like lots of ideas on how to have a vintage wedding and use vintage items for decorations, favors and more order a copy of The Everything Green Wedding Book where you'll find plenty of vintage wedding advice and some DIY ideas.