Maybe a gown with a low back that shows off the tattoo on the spine, or experiment with non white dresses -- personally I think a dress in a dark color, like black or chocolate or navy, would look stunning, and show them off. The problem for me with most tattooed brides in traditional dresses is that they just don't look. . .well, traditional.
I guess what I'm saying is that on all of the dresses above, my eye immediately goes to the tattoo instead of the bride. That's the risk you run, frankly. So I would try several different types, styles, including ones that aren't wedding-y at all, to see how comfortable you feel. The most important thing is that you feel comfortable with how you look and how you present yourself. Give yourself enough time to try on a broad array of gowns, including ones that cover the tatts up, and go with the one you really feel the most comfortable in.
