Advertise in tattoo and peircing magazines/websites....posters/flyers the usual stuff really.
Don t open an ebay store.Just advertise a few using regular auctions.When I go into eBay right now and type tongue bar, I get 572 listings. *None* of these are from eBay stores as those *only* show up on a search if there are less than 30 hits from reguarly auctions.So if you had a store, you d pay $16 a month, place the auctions and get zero sales. If would be cheaper to pay for a listing that might actually get seen.
Write a blog about your ebay store and bookmark it in several locations like facebook, myspace, blogspot, Digg and other sites.