@Reedyn for now you can insert images using a URL with markdown expansions.  will create an image card that is linked directly to the URL.
We have plans for an extensible image selection system, likely including Local File, Unsplash, and URL to start but having the ability to add custom file stores that we can re-use across the admin. Unfortunately it’s unlikely to make it into the first version of Koenig due to time constraints but it is definitely on our radar.
One of the big questions still outstanding is how such a system would tie in with a thumbnailing/resizing service so that we don’t end up with inconsistent behaviour depending on where an image is sourced from.