New
#31
This seems to have been changed/fixed in the Fall Creators Update. I now reliably see the current Spotlight picture on a restart or a cold start in 1709.
BTW, if you ever do see the default Windows start up picture, it's not the 'cave' any more. The built-in pictures are found in C:\Windows\Web\Screen. The 'cave' is still there, but the default now appears to be img103.png - a lake in the mountains (the 'cave' is img100.png).