I updated the language file download Thanks for the input @Vitaro
FYI: The flag for each language is saved in the *.locale File as base64 encoded binary data.
If you don't want to (or can) save the flag to the locale file, just place a small *.png file of the flag (about 25x15 px) with the same name in the folder.
I did this for fr, ru and es now.