Ubuntu – Language support
sudo apt-get install language-selector-gnome
reference: http://askubuntu.com/questions/331515/language-support-icon-missing-in-system-settings
Install im-swtich
was the problem for me. So this fix this problem. sudo apt-get purge im-switch && sudo apt-get install language-selector-gnome
then login and logout and the language icon should reappear in the system settings.