As I already mentioned in your previous question, setting the post per page will not help you. However, there is a workaround.
Instead of directly setting the post per page, use a variable and change that. Then use the same variable to slice the array. For example:
$per_page = 2;
// Use the $per_page value to set the posts per page
$args = array(
'posts_per_page' => $per_page,
);
// The rest of your code here
// Now, before returning the images, slice the array using
// the variable we set before
$images = array_slice($images, 0, $per_page);
return $images;