Yes, the preload list file is read in via PHP server side and then the client side JS code kicks in and uses the PHP variable $image_paths[$image_counter] like so "<?php echo $image_paths[$image_counter] ?>".
The PHP variable passed over to JS has the right values which I've checked via alert('<?php echo $image_paths[$image_counter] ?>');
So if your question is what I see in the browser, my answer is nothing unless I explicitly tell the browser to show me something (i.e. do a PHP echo or JS Alert). There's also no error messages.
P.S. The above code is placed within a .php file. The PHP is fine, it's the JS that's tripping over somewhere/somehow.