Pareidolia is a phenomenon where people see images or hear sounds in random places. The idea that there are secret messages in certain songs that are played backward is a common example of pareidolia. Many people who believe they've captured ghostly faces are also victims of the phenomena.
In 2004, Diane Duyser sold a 10-year-old grilled cheese sandwich that looked like it had Jesus on one of the pieces of bread. It went for $28,000. Religious figures, like Jesus, commonly pop up in foods like chips, bread, and even Cheetos. People end up making quite a bit of money off of this scientific happening.
The Rorschach inkblot test is the most common practice in for pscyhoglists to help get an insight into what the psyche of their patients looks like. They use pareidolia to get patients to tell them what they see in random inkblots.
In the paranormal community, this happens quite a bit. Someone will take a photo of a house and think that they see a face in the window. This usually happens because they're looking for something like that to show up, especially if they believe in ghosts.
A lot of the time, if a paranormal enthusiast believes that they have significant evidence in a photo, they'll have to draw an outline of what they're seeing.
The human brain is great at imagining things that aren't there. That's why pareidolia is so common. The brain will make people think that there are faces in random swirls on a mirror or the grainy blackness of a photo taken at night.
People will see faces in virtually anything and call it paranormal. It's up to you to decide whether it's real or not!