Here's an example: https://domains.google.com/thumb?u=http://500px.com/photo/78702255/lone-tree-of-wanaka-by-james-gladwin. Unfortunately, the URL only works if you are logged in to a Google account and Google Domains is enabled. There are many other services that generate site screenshots: ShrinkTheWeb, PagePeeker and more.
Google Domains is still in beta and requires an invitation. It's a service that allows you to register domains and manage them.