copyright.png exists in /w/resources/assets/licenses currently (and has existed for quite a while), and since that directory is de facto controlled by upstream, that one image gets lost during major software upgrades and bringing it back is mildly annoying, when we could just simply place it in some different directory and update the references to it in individual wikis' settings to avoid that extra hassle.
For reference, some of the relevant SVN-era commits: rSHWK3309, rSHWK3877, rSHWK4273, rSHWK4303, rSHWK4323, rSHWK4377, rSHWK4566