Rounded buttons everywhere... here goes something kubical ;-)
Just kubes. Green for glue, yellow for minimize, orange for maximize and red for close...
This is an IceWM window decoration (unfortunatelly i don't know, how to create native window decoration) which goes in steps of the same named wallpaper.
Unpack to ~/.kde/share/apps/kwin/icewm-themes.
(Read the default.theme file for notes and theme variations...)