Thanks for the answers !
When I was mentioning "high quality" I was thinking more in the range of 3000+ pixels wide. I also agree that images that size are not fit for general web display but more for download, either as screen savers/backgrounds or for study purposes.
Even in the 1000 - 2000 pixel range, it looks like not all the artists enjoy the same popularity on the internet, for example
Miro
It's a pity that sites such as the
Web Museum haven't really developed. How nice would that be to be able to browse all these paintings in the comfort of home rather than standing in a museum. This would also allow for a richer experience, by being able to get more information about a particular artist or topic from Wikipedia ...