Is somebody aware of an extension to display any url?
This url could be set in the options of the extension.
Obviously the extension would then display a downsized image of the site at that url...

I am sure this has been made, but I cannot find it...

I don't see this kind of extension on chrome extension repository too. Maybe I could write one but I don't really know what thumbnail provider I'm legally allowed to use. It seems "http://www.thumbshots.com" could do the trick since there are 2 firefox extensions using it...