I'm also starting to plan a 30 gallon hillstream biotope. I am thinking either Assam, Darjeeling, or Yunnan, because those are my favorite tea-growing regions.
A Darjeeling tank would revolve around rosy barbs, zebra danios (or mustached danios, D. dangila, if I can find any), and various smallish loaches. I'm having trouble finding much info on the Assam and Yunnan areas. Yunnan borders on northern Myanmar, which has some very interesting fish, so I'm fairly hopeful about that one.
A mountainous-looking backdrop will be needed, and it probably will need rows of anubias to simulate tea plants.
This is all just a twinkle in my eye at this point, but I know in another year or three I'm likely to get tired of the Sumatra rice paddy and be ready for a change. Doesn't hurt to plan ahead.