Who are the people in MS Office wallpaper?

We recently had our work computers upgraded to Windows 10. Now, on the start-up page where we are prompted to “cntrl-alt-delete”, the default background is one of a few nature photos. One appears to be looking out of a cave to a beach. Another - which seems to have become the default on my computer - is of a mountain lake.

When you look carefully at the mountain lake, near the bottom to the left of center, there are what appear to be backpackers - or at least a couple of backpacks.

That got me thinking.
-Why did MS choose THESE SPECIFIC photographs, to be their default wallpaper? I wonder how many folk spent how much time deciding these were the BEST photos out of the zillions available?
-Assuming that the photos were not chosen at random, why did they choose one with apparent human activity in it?
-Who ARE these backpackers, and did they have to sign releases?

As should be abundantly clear from my tech posts, I’m pretty tech clueless/simplistic. I could not care less what my start-up screen looks like - any more than I care what color handle is on my hammer. But I right-clicked to see what other stock backgrounds were available. One of those had a beach scene, with a woman running on the beach. Same questions - who is that runner, does she know she is loaded onto countless computers, etc.?