So, installed the Yosemite update yesterday, hoping it would cure the screensaver problem. All it did was make the problem consistent -- now does the same thing on my MacBook as on my iMAC (reverts back to NatGeo on screensaver). Suggestion by someone to try vintage didn't work either.
Scupper76 and dotdotdot, I'm having the same screensaver default back to natgeo, but I can't find vintage in the screensaver area. I tried the "help" function, w/no help. Can you tell me where that vintage option is in MacOS X?