Crazy idea, but I'll throw it out there. What if we display a link to various image searches when we have no free image available, like we do for ISBN's now sorta. It would be super easy.
{{image search}} click to expand, and have a few links:
http://images.google.com/images?q=%7B%7BARTICLENAME%7D%7D http://flickr.com/search/?q=%7B%7BARTICLENAME%7D%7D&w=all
etc. Maybe even include the [[replace this image.svg]] thing in that same template, nice and simple.
And for the record, I don't think it's a minority of people that want Wikipedia to have primarily (if not only) free content.