Individual leaves extracted from this photogrammetry scan:
https://www.artstation.com/artwork/w8JOm9
The meshes are one sided, but I did try to create interesting translucency maps to make them look appealing. I also used a method of RTI (Reflectance Transformation Imaging) on the sycamore leaf, which is just a material mapped to a billboard.
Material - Autumn Sycamore leaf