Spirited Away: Tunnel WIP

I've been so flip floppy on my Spirited Away projects, I did some work on the tunnel scene today.

Just a quick post, I'm 85% finished with the modelling  and had fun playing around in PS to make textures.
The trees are from Onyx and the bushes are PaintFX presets that have been tweaked to hell and back to look decent. This time I'm rendering with Mental Ray Physical Sun & Sky since Arnold wasn't liking the opacity maps on my leaves... hm.

Render time was 5:44 for 960 x 540, not bad! I expect vast improvements on render time once I turn the foliage into proxies.

With grass:

The grass looks pretty crappy, I applied it just by painting directly on the ground, but I am looking to using particle instancing to distribute it more naturally.

UPDATE:

Here is a preliminary look at some bush instancing. 4 different bush types that are instanced to fill the background, I will hand-place extreme foreground foliage. Render time was about 4:30 at 960 x 540 without optimization (though render time increases the closer the camera gets to the foliage).

What is frustrating is that some of the bushes are floating above the ground plane even though the pivot of the bush is at the bottom of the trunk, its at the origin, and transforms frozen... hmmmm.

Some of the textures: