With InputfieldCKEditor there used to be the pwAssetPageID property that could be added to the Custom Config Options in the Input tab. It let you define a page whose image field was used by default when clicking on the Image button in the editor.
This was very handy if you wanted to embed recurring images from a central page instead of uploading them to each page where you needed them. (I think the feature stopped working at some point, however.)
Is there a way to achieve the same behavior with TinyMCE?