What's some good content for a background/ambient projector display?

I have a spare projector; generic <$100 one, so it does reasonable video and larger displays, but you wouldn't want to be reading fine text off it.

I'm considering using it as an always-on background display for "ambient" purposes (more decoration than information radiator) in my home work/play/create space. Display hitting a wall off to the side, driven by a PC or Raspberry Pi, custom code if necessary.

Looking for ideas for content to display on it, beyond the obvious slideshow of random photos or generic nightclub-esque visualizations.

Don't have anything specific in mind - probably something dynamic, maybe data-driven, connected, more so than pure art. Assume similar tastes and proclivities to the usual HN demographic.

Any ideas?