To avoid excessive traffic to your site, we need to cache your image/CSS/JS files on our servers. If you modify the file contents on your end, this won't update it on our end. This behavior is expected as it's a common practice in many other caching solutions (CDN, browser caching, etc.)
To force NitroPack to download the new file, you can either:
Save the file with a different name, and update your site content to use the new name.
Do a complete purge of your NitroPack cache, forcing our service to re-download all resources.