I'm doing map commissions on DeviantArt, and I got a rather difficult request on my latest commission.

First, here's the example map that the commissioner provided me with.

I knew looking at the map and reading her requests that it would be difficult, but I took the job anyways because I need the money. I've been given permission to sort of fill-in an unspecified areas with what seems appropriate. So then, onto her requests (paraphrased).

The area labeled forest is to be filled with trees up to the border.
The chemical area is where a laboratory is located, so its not chemical like everything is dead.
The area labeled city is to be filled entirely with buildings.
Not colored, kind of like ink on parchment.
Setting is modern, japan inspired.
I already have the desert and mountains finished, those were easy. The forest is almost done.

But I'm really drawing a blank on what to do in the chemical and city areas. Any advice, brushes, patterns, et cetera someone can point me towards?