Currently, when using Image Field Type, the Editor can only upload a new image file there, which cannot be reused in other Content Objects.
It has been suggested that it would be better if adding an image to Image Field Type would work similarly to how adding an embedded image to RichText works. This means that it would need to be possible to select/create an Image Content Type via UDW.

The current workaround is to use the Relation Field Type instead of Image Field Type.