lightdm-gtk-greeter power and settings indicator show no icon

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http://askubuntu.com – I installed Ubuntu mini 12.10 and then I did apt-get install lxde-core lightdm-gtk-greeter. I successfully changed the LightDM screen resolution editing the /etc/lightdm/lightdm.conf and adding display-setup-script=xrandr -s 1280x720. How to add an image for the power and settings icons in the lightdm-gtk-greeter screen? Right now, it looks like this: (HowTos)