Hello Ben Alexandra,
What we have done to address this request is provide filesystem storage providers for Libraries, which allows you to have your images, videos, etc stored on the filesystem, but at the same time appear in Sitefinity Libraries. You can learn more about the functionality on this article form our Documentation
. If the above does not suit your specific use case scenario, please check this forum thread
which contains a long discussion of similar functionality requirement. I've provided a sample extension of the RadEditor with a custom dialog allowing you to browse the file system and insert links to documents and specify custom title for the link. You might take a look at it and try the sample source code I've provided and modify it slightly, so the inserted HTML is not <a href> but <img> tag also you can find more information on adding custom dialogs to RadEditor on this article
from our Rad Controls documentation.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items