Thanks Hannes. I agree that most trees have too large leaves. But it's all to do with file size I guess; with smaller leaves you need lots of them. I tend to make/photograph complete branches as well. In Speedtree you can even make a variety of them from several leaves and stems and save them as a branch image.
If I may break into your thread; there's another thing I thought of lately. The alpha is usually a hard edged grey image. If you soften that up (considerably) TG will (for the time being!!!) read it as hard, but if you then add a PF it may be broken up on the dges, which might give nice results (decay). I still haven't tried it though.