A mix of Yvonne and Elaine, Yvaine was first noticed in the Neil Gaiman fantasy novel and then movie Stardust, in which Claire Danes played the 'fallen star' Yvaine. It is now attracting namer attention--just as that other Gaiman-inspired name, Coraline, did. Yvaine has a definite romantic, medieval charm. A small segment of namers are definitely taking notice.
The name probably derives from the Arthurian male name Yvain, one of the Knights of the Round Table