I've seen a similar thing used to generate low-size versions of images using arbitrary SVG primitives (large triangles or circles rather than small blocks), for use as placeholders while high-res images load. I can't find any of them in quick search, but there were a couple of F/OSS tools that implemented the trick.

UPD: found one of them, https://axe312ger.github.io/sqip/ (look at the “SQIP primitive art” column in that page's examples table)