What do you call these pictures / illustrations? I have seen a few pictures like this one, but I never found out what to call them:

Artwork by Matei Apostolescu
It doesn't necessarily need to be this abstract, just a detailed illustration, where lots of things are going on or are just present (perhaps I'd compare it to Where is Waldo illustrations).
What key words to use if you want to find more pictures like this one?
In german it can be called Wimmelbild. That's usually for kids, where they can find stuff, think you call it where's wally in english:
https://de.wikipedia.org/wiki/Wimmelbild
Here is some discussion about the word:
https://dict.leo.org/forum/viewUnsolvedquery.php?idThread=706597&amp;idForum=1&amp;lang=de&amp;lp=ende
They call it &quot;crowd scene&quot; or &quot;illustrated panorama&quot;.