Display flags to switch languages. This plugin only uses the locale files from wordress or buddypress and eventually your theme.
This will be the default language you mentionned in your wp-config file.
You can find other flags on http://www.famfamfam.com/lab/icons/flags/. Don't forget to rename them after full WordPress locales (ie : fr_FR.gif)
No, this plugin only uses the .mo files loaded in your wp-content/languages and eventually your buddypress and theme directories.