Gnuite,

Take a look at this French website; the tiles appear to be organized in Mercator Lat/Lon, but with an alpha-numeric referencing system. The Topo maps and imagery are top notch though.

http://www.geoportail.fr/visu2D.do?ter=metropole

Image tiles are like this:
http://visu-2d.geoportail.fr/geoweb/maps8u6m2GpH0.jpg

Also found this http://thepochisuperstarmegashow.com...cts/#geopochi2 a tool that reads the tile into GEarth; would it be of any help, since this guy has cracked the tile naming convention?

Cheers