An Image screen object associated with an image field can still be used on brief display screens for Collections instead of a normal entry field, but it will be represented by a thumbnail column in the Result set. If there's no field with the reproduction reference tag of the list screen, then the user can always select the image field from the Result set settings dialog to still display thumbnails.
Image objects have no use on detail screens for Collections and will be ignored: the Collections Media Viewer is automatically present if there are image fields in the .inf associated with the current data source.