after i executed
unity-greeter command in terminal, my theme changed into classic gnome and my icons too.
and even some of my icons have been deleted !
i tried to change some files like
/etc/lightdm/unity-greeter.conf to change defaults of my session but it was useless .
can anyone help me to revert my settings back ?
Check the answers to a similar problem I had. Quoting from there:
Hopefully it will solve your problem as well.