is in the eye of the beholder. Chose yourself what you think is beautiful.
Personaly, I like names with mostly voiced consonants. In other words with B, L, M, N, V, Z.
Isabella, Linnea, Veronica, Anna, Linda, Lydia, etc. sound very nice and roll off the tongue, but might not be too German.
Please stay away from names that have a lot of hard 'G's or 'H's.
Gertrude, Gunhild, Gretchen, Hildegard, Helga. They are ugly (to me) and sound like some stupid opera singer.