Here is a foliage study. Using multiple models and colors, I set the foliage in a "bubble" configuration, to where there are smaller and more instances on the edges, and larger and less instances in the middle (based over 3 different size ranges, each with its own 2:1 size range). This is all mapped with a power fractal and with slope constraints. I think it looks pretty realistic.
The trees were all made with Dryad. Honestly, I am starting to really like that application!
Render time was horrendous! It took nearly 80 hours @ 800x600, quality 0.8, AA 10. This was over 4 cores, so a single core would have taken nearly 300 hours! This is much too long and I can't wait for the next TG2 updates.
Part of this killer render time has to do with the surface effects on the leaves (which includes reflectivity/specularity, translucency, and even a hint of luminosity). Additionally, I used an earlier version of the new fractal stack surface (the one to RULE them all). I want to post a test render of this surface...its amazing, but HUGE and actually takes a while to render by itself!