Here's a link to World Art treasures, it's worth a look just to see the collection of images. The are listed by artist or period, also by country, region , city.
So far I've only looked at the prehistoric art , beautiful examples of cave art. Lots of analysis info in the section marked " Essays and contributions by others".
Christine Besack :)
"A shared Vision comprises the collection of works of art built up by Jacques-Edouard Berger and now on loan at Lausanne's Musée de design et d'arts appliqués contemporains, together with essays linked to his passion for collecting."