I love Felix and Ivy. No need to look further, in my opinion.
But, if you want others and you feel many of the obvious candidates are taken then maybe something with a classic feel but unusual:
Ariadne, Aurelia, Araminta, Alanis, Alessandra, Belinda, Bronte, Cassandra, Calliope, Clarissa, Calista, Cordelia, Camilla, Carolina, Catriona, Danica, Davina, Diana, Evadne, Elisaveta, Elspeth, Fenella, Genevieve, Giselle, Henrietta, Honor, Isadora, Inez, Jacinta, Judith, Jocelyn, Katherine, Lorelei, Larissa, Leticia, Lavinia, Liliana, Miranda, Meredith, Melissa, Natasha, Natalie, Naomi, Octavia, Ophelia, Philippa, Persephone, Pandora, Paloma, Rhiannon, Rosemary, Rowena, Samaris, Susannah, Saskia, Tamara, Talitha, Vanessa, Vivianne
Alistair, Adrian, Benedict, Caspian, Christian, Cyrus, Dominic, Elliot, Edmund, Fergus, Jeremy, Jeremiah, Jesse, Kester, Leonard, Michael, Noel, Orson, Patrick, Ptolemy, Peter, Quentin, Richard, Robert, Rupert, Ralph, Solomon, Simon, Timothy, Titus, Victor, Vincent, Walter