Susannah is a great one. I think Diana is due to be part of the early 20th century revival. Philippa, Francesca, Lydia and Julia/Juliet might be getting a bit popular for you.
Serena, Louisa, Claudia, Cassia, Caroline, Cosima, Frances, Lois, Adela, Edwina, Henrietta, Hermione, Ismene, Iona, Ione, Jocasta, Catrin, Jocelyn, Leonora, Marina, Octavia, Persephone, Perdita, Rosamund, Rosanna, Annalisa, Christabel, Seraphina, Teresa nn Tessa, Yolande, Estella / Stella, Oona, Honor, Flora, Genevieve, Gwendoline, Cassandra, Margaret / Marguerite, Davinia, Octavia, Annis, Lucinda, Lucienne, Vivienne, Victoria, Viola, Miranda, Verity, Constancia, Rosaria, Georgiana, Camilla, Laura