You can customize the pre-loader for product gallery. You can blur our the other gallery, fade out the other gallery and Grey out the other gallery. You can also customize the spacing, paddings and margins between the product thumbnails.
Some demo Pre-loders are given below,
Grey Pre-Loader Demo
Fade Pre-Loader Demo
Blur Pre-Loader Demo
There are other technical functions in this plugin too, such as
There are more and more customization options available that you can check from here.