Tableau release notes "Image objects can now link to web-based images, as an alternative to images inserted in a workbook. This is particularly advantageous for large images, which load much more quickly when hosted on the web. (By contrast, inserted images must be downloaded every time a sheet is opened, slowing performance.) Linked web images also allow you to use animated GIFs, which Tableau doesn't natively support."
Connected authoring for web edit: New in Tableau 2021.2