With a little imagination you can make a zoo of your very own. Start collecting all shapes and colors and sizes of leaves wherever you go. Press the leaves between the pages of a large book as soon as possible. Then all you need besides the pressed leaves are paper for mounting and glue.
There’s no need to make preliminary sketches of your leaf creatures. Just be aware of the color, texture, and size of leaves. Spread newspapers on the floor and scatter the leaves around. Then see what kind of creatures you can create!