Even as I was writing this I kept finding more things I didn't notice on my first few passes through the cities:

Phyllis fades from color to black and white except for two houses. The fairground has a big top with tiny bleachers and a guy inside. The happy city has people with their arms raised in a V. People in the marketplace city wear hats and some are carrying bundles on their heads. There are weird cactus plants in the hanging city. In the half-fairgroud city, there's a statue on one of the trucks. The city that copies the dead has a set of pallbearers carrying a wrapped corpse down the stairs. The people on top of Argia are laying with their ears to the ground, listening for the animated sound waves coming from below.

And on and on and on and on. I just can't even.