Hey, I thought I'd put my 2 cents in on this topic. I've done a fair amount of experimenting with this. It is not necessary to edit the text file, a new leaf put in the Data - Plants folder will automatically show up in the drop down in Carrara. I believe the best way to create a new leaf is to model the shape as simply as possible and then apply the texture with the UV editor in the vertex modeler. My experience is that using a transparency to create the shape is unnecessarily cpu intensive. This test render has 2 custom leaf shapes and some other modified stock leaves. falconperigot is right, if you model the stem Carrara will be able to detect where to attach the leaf.