are you try it with [url] parameter?
<style>
<?php
$residential_images = get_field('residential_gallery',29);
$residential_image_end = end($residential_images);
reset($residential_images);
?>
.scaleme#residential{
background-image:url(<?php echo $residential_image_end[url]; ?>);
}
</style>
for test it:
print_r($residential_image_end);
