I used buttercream icing. I used cookies cutters for the leaves and acorns. If you just lightly press down on the icing, it leaves the outline of your shape, and you can fill it in with a star tip.
For the veins on the leaves, I just piped icing on top of the star tipped leaves, until I got the right look.
My border needed some help. But all in all, I was pleased with the way it turned out.