I used old books to flatten my leaves and mounted them on card stock. Below are photos of my leaf artwork.
The cow is one of my favorites. The head is made from a Tulip Poplar leaf. (I optimized the photo for quicker web page loading, and lost some color depth in the image.)
The narrow leaves on the butterfly are from a Willow Oak. The dark dots were punched from a leaf.
This aquarium scene has an oak leaf representing seaweed in the bottom right. Remember that White Oaks have rounded lobes and Red Oaks are pointed.
This parrot is perched on a branch made with fern leaves.