Go nuts with CSS3 hover effects
Why is everyone shitting on this in the comments? It's a demo: you can't complain that it's hindering usability or enjoyment of the pictures when there is no context in which you might use it or enjoy the pictures. When I saw this I thought it might be nice for the website of a magazine like vogue or something: some sites are about decoration and style, usability can be at the back of the priorities. Just because it wouldn't survive A/B testing on the landing page of the most recent groupon clone doesn't mean it's not useful, cool or fun.