In rare situations during an initial install or upgrade of the Carousel software the mime type for scalable vector graphics (.svg) can go missing, causing some UI elements and icons to show as broken links.
The image below shows the UI in error on the left, compared to what is expected on the right:
Log into the Carousel server's desktop and open "Internet Information Services (IIS) Manager." Under the connections panel on the left expand the server name, then expand sites, and click Default Web Site. In the features view panel in the middle double-click "MIME Types."
Scroll down the list of MIME types and ensure that .svg is not listed (ignore .svgz as it is a different extension). Click "Add..." under the Actions panel on the right and input .svg for the extension and image/svg+xml for the mime type, as shown below:
Press OK, and restart IIS be clicking the server name in the connections panel on the left, and then restart in the actions panel on the right.
Refresh the login page and the images should now appear as expected, some browsers might require a restart or clearing the cache and reloading the page (Windows Chrome/Firefox: ctrl+F5, macOS Chrome/Firefox/Safari command+r).