Yes, this is not possible. Besides that KDM in theme mode doesn't support user lists at all we won't see a transparent user-list before KDE 4 which is based on Qt 4 which supports semitransparent widgets (in fact a full alpha channel) natively.
-- transparent user-list background for KDM https://launchpad.net/bugs/53620 -- kubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs
