I considered it in the past, but left when looking at the large amount
of files without copyright tags.
The problem of
mediawiki.org is that they have many files whose
copyright status is unknown, but that -unlike wikipedia- were uploaded
by there authors (with high probability).
There are old files with unactive authors which would be a pity to lose,
screenshots including logos, files with no license by wmf employees...
However, I think it's a good time to begin being strict with the license
of newly uploaded images.
Happy New Year!