The falling leafs were created using a texture with an alfa transparency on a box with sloping edges ensuring it will look natural from all angles when falling and also when landing on the ground.
Fish swimming in a circle were created using the force over lifetime and rotation over lifetime on a particle with a fish mesh. Now knowing how to use the built in animation system in Unity the same result could probably be created with much less effort. Making the particle travel a circle with the force over lifetime curves while also rotating it at the correct spots was a bit time consuming.
Niklas Johan Larsson 