Hi, just found this on https://transposh.org/faq/ :
In the languages array in the constants.php file change the two letter ISO code used for that flag
For example, to change the flag for the English language from the stars and stripes to the Union jack find the following line
‘en’ => ‘English,English,us,en_US’,
And change it to:
‘en’ => ‘English,English,gb,en_US’,
Note that this works out of the box only in the non css version of the widget, to make this work in the css version you will have to modify the image used.
Hope this is helpful.