Tiffani is one version. Another one is Tyffaney or Tiffaney. Other popular versions include Tyffanie and Typhani. I've also seen Typhannie, Tiffini, Tphany, Tphanie, and Typhanie. Any embellishment you can think of for the name Stephanie would work here, too. I've also seen the double "ee" at the end of all of these, like Tiffanee, Tyffanee or Typhanee.