I have never seen this before (which probably means it has been around for 2 years),
but at
the background was like a video of some sort. I was expecting a full picture background but then people started walking around and I realized it was a full background seamless video maybe?
Sadly PayPal takes me to the UK home page that doesn’t have the video but I know the effect you mean. This site also makes great use of background video to provide the snow effect in the top panel as well as a team shot lower down the page;