I think the technique is called pictogram or pictograph where the image is recreated with other images or a shape, pattern, whatever. You need a plug-in or perhaps a separate application altogether to create the image.
There is photo mosaic software that can do this, you would load a folder of traingle/diamond type images rather than photographs.
Also embed an image, and try filter >> create >> object Mozaic. The result is all squares, but believe you will find this often forgottten filter interesting.
You may be able to create something like this by following and experimenting with the techniques outlined in this tutorial:
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