This is hardly a concern. First because you’re not limited by Webflow on the space your site takes. Also, images are only downloaded when they’re needed. But the main reason is that even if the files of your website are physically gathered in a foilder on some server, the image aren’t. They’re with a ton of other images on some cloud server at amazon (look their URL). Removing an image from the CMS don’t make it disappear right away. Clouds have rules that us mere mortals don’t understand sometimes.