So, the picture I posted ... yes, both stumps / log ends. The wood stays damp, thus charcoal-gray instead of white, because of the spray coming off the little rapids. Parts are covered with almost black bark which creates the appearance of spots that could be face features. Finally, the sun broken by the mixed shadow of overhead trees really adds to the appearance they are something more than they are.
I did not see those "shapes" when I was taking the pictures. I only saw them when I was reviewing pictures later. They were interesting enough that I had to go back despite it being about a 5 hour round trip drive.
Pareidolia is not an inherently bad thing, it's how our brains work to process images comparing the inputs from the environment to "saved keys". It's how we knew the thing behind a bush was a tiger without seeing the whole thing, we see enough to reconstruct the pattern and run for our lives. From my perspective as a computer geek, the image processing our brain does is fascinating. Unfortunately, as I age I slow down ... I can actually see the processes occurring that used to be so fast they seemed sub-instinctual. That dang tiger might get me yet.
MIB