Rosamund reminds me of a sort of pastry or cake. I imagine a plump sort of person, too old-fashioned for my tastes.
Genevieve is rather pretty, I suppose, no opinions here on punctuation.
(It remains pronounced Jenna-veev in my head.)
Himiko is different. I don't have anything against Japanese names, but the -ko ending brings to mind a child (of course). An endearing child, but a child, just the same.
It sounds kind of like a flimsy, fragile sort of name. I don't know.
I wish you luck in your decision!