Although your question appears to be about an xml feed for library images, the process to display those images on a page requires use of a template with a special query to look for ‘attachment’ type pages, which is how images are stored in the database.
That’s a bit more complicated, but I did something similar in my ‘Multisite Media Display’ plugin, which uses a shortcode to display media images on a post/page. Works on single and multisite sites. Plugin is here https://wordpress.org/plugins/multisite-media-display/ .
Since plugins are open-source, you are welcome to dig into my code to see how it’s done.