What's the name of that...Whatsit?

Pariediolia is the name for the native human tendency to construct faces out of random patterns. Like Arcimaboldo's work, but by chance rather than art.

The word comes from the Greek for something like "wrong image."   Spotting the face of St. Lucia on your flatbread pizza  –– mental illness notwithstanding –– is bonus in our evolutionary heritage of pattern recognition.

It's related to the way that when confronted with a paper plate decorated with bull's eyes, a wee bitty baby serves up the same charming goo-goo eyes for the plate as he gives to actual human faces. Survival of the most charming.  

Which tells me that the point of imagination is to actually and genuinely save your life.
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But what's it called when you spot horses everywhere?

The local osprey population LOVE using scraps of black polyethylene from construction sites for their own building projects. Naturally, it gets away from them. They don't use nearly enough fasteners. We end up picking a bale of this stuff off the lawn –– and out of the trees –– every January.

References
https://www.psychologytoday.com/us/blog/reality-check/201111/11-11-11-apophenia-and-the-meaning-life

​http://www.slate.com/blogs/how_babies_work/2013/04/03/babies_and_the_new_science_of_facial_recognition.html