I can get the ones Wikipedia has through the URL given by Geonames. Thing is, I may get a little money through Google ads, and these Wikipedia images may not be for those people who make money through their websites. Of course, I wont be selling the images at all.
For the big images we would need to extract images that are put under a 'public domain' license by the copy right owner. Unfortunately I have not yet seen a dump of meta-data (image license) wikipedia dump that could easily be parsed.