Have a look at other GTK themes, icons themes or window borders. There is a theme called 'Adwaita' available in the Canonical PPAs which might help you. To install it, write "
sudo apt-get install gnome-themes" (not sure of the package name) in a terminal. Otherwise you can search other themes on the Internet. You can find some themes on Gnome Art or on WebUpd8.
You can also use Ubuntu tweaking tools (Ubuntu Tweak, MyUnity, Gnome Tweak Tool and the newcomer Unsettings) to customize your theme (Icons, Window Border, Theme...). Perhaps there are combinations which respond to your needs, who knows ?
EDIT for Tweaking tools : there is also the
com.canonical.unity-greeter entry in the dconf editor (and the dconf editor in general).