Get control panel asset thumbnails into a frontend template
There's actually a really easy way to achieve this (Craft 3 only).

Simply do this in your code:

&lt;img src="{{ image.thumbUrl(int) }}"&gt;

{# int is a number that represents the width/height #}


The asset thumbnails are stored in /storage/runtime/assets/thumbs/, so no, they won't be taking up space in your S3 bucket (whereas some local testing inclines me to think that images generated via transforms are stored in your Asset Volume, wherever it's located).