For a while, I've had my standard computer background: the original R2-D2 and C-3PO concept art by Ralph McQuarrie. I like because it has a mid-century futuristic feel, and because I'm a nerd.
But I didn't have a good screensaver to fit in with the mid-century vibe at our place. That is until I looked over at a co-worker's monitor while he was at lunch. He has a great flip clock screensaver, which I now have on my home computer.
retro flip clock to match.