The new code supports different caption text for each language, but not different images. That said, it might be possible to have a different instance of the fadeshow for each language, each with its own set of images. Or you could add some coding to jscript_fadeshow_setup.php to set the image for the fadeshow depending on the language, such as replacing

["includes/templates/your_template/images/yourimage0.jpg", "", "", "<?php echo FADESHOWTEXT_1_IMG00;?>"],

with

["includes/templates/your_template/buttons/<?php echo $_SESSION['language'];?>/yourimage0.jpg", "", "", "<?php echo FADESHOWTEXT_1_IMG00;?>"],

and saving the images like
/includes/templates/your_template/buttons/english/yourimage0.jpg
/includes/templates/your_template/buttons/english/yourimage1.jpg
/includes/templates/your_template/buttons/french/yourimage0.jpg
/includes/templates/your_template/buttons/french/yourimage1.jpg

There are other similar ways of doing this as well.