Files which are copied from a copyrighted source are a continuing problem on Wikipedia. At the moment, there is not a possibility to standard hide images for which copyright status is unclear, or to exclude such images from certain pages (or namespaces).
I would consider to include keywords as NODISPLAY and DISPLAY for images, where the NODISPLAY tag is standard for images, overridden with DISPLAY when the image is properly tagged for the correct copyright (either by using the keyword, or by proper templates which transclude the keyword). That would make images which are not carrying any text standard be not displayed UNTIL they deliberately are properly tagged. It somewhat enforces editors to go that extra step and do an attempt to properly tag images they upload.
In combination with this, non-free material which can be used under fair-use criteria could be tagged using DISPLAYMAINSPACEONLY, resulting in all images with that tag to NOT display when they are in e.g. drafts in the user-namespace, but 'magically' appear when they .
This could also already prepare for possibilities to tag images as 'offensive', 'sexual content', etc., where users can override the display of such images by user settings, or so page-code can do something with such images, when a wiki would consider to give that possibility.
Additional thought is to make the images display in edit-mode, so editors can see how the page renders with the images, but that they do not display normally (which again may be useful when working on userspace drafts).
Note that it needs to be taken into account that images may be hosted on commons, but transcluded on e.g. foo.wikipedia, if foo.wikipedia wants images properly tagged (and not-display when they are not properly tagged), whereas bar.wikipedia may not care about the tagging and just display.