Sorry I couldn't reply earlier, been very busy lately...
First off, the industrial age looks absolutely stunning in its finished state. Also, your addition of the trees to each era is absolutely beautiful. RA, you keep out-doing yourself with each detail. Very, very good job!
Secondly, as I promised, the pictures of modern Japan. I believe this will the be the trickiest and most difficult of all eras, but I hope you're still up for it.
The reason this will be more difficult is because there won't be much transition from a small Japanese town to a big bustling city. You'll see what I mean.
Small Japanese City:
Pretty basic, the small towns in Japan are basically just tiny housing communities. Just make a couple dispersed houses (keep in mind the slightly more modern architectural look compared to previous eras), and maybe a convenience store. (the first of the village pictures is an HDR image so it shouldn't really be THAT colorful)
Medium-sized City:
For this I would propose adding a factory to the scenery. Would be very fitting for a medium-sized city. Maybe also a mid-sized building looming over the houses around it. And a small shopping area, something of a strip in the center or so.
Japanese Big City:
This is where it gets tricky. An abundance of tall buildings everywhere, a highway running there, a railway here. Electro masts sprawling through the place like wild. See what you can come up with, the images are there for your reference. What I would very much like to see is the Mori tower (the tower of which multiple images are attached, though if it proves too complicated, it's fine if left out). If it's possible to have the highway cutting through the city, that would be great too (reference to that is in the fourth picture). And don't forget a sh..load of signs everywhere. The Japanese seem to have a fetish for those. There should be enough building referencing for you to work with. I also gave you some skyline pics to try and imitate. Also keep in mind that the Japanese use very interesting and unconventional architecture for the buildings, try to bring that into detail. Good luck hehe!