The falling leaves do look copy and paste... because ... well...that's pretty much what it is.
If you want to do the falling leaves, you should look into creating one movie clip, a leaf, which is displayed falling in random positions and sizes. That approach would be much more realistic.
There are a number of tutorials that show how to create "Fire Particles" in Flash. A single flame is distorted and moved using mathematics. One tut is available somewhere on:
www.learnflash.com
Google for the exact address. There are many others also. Change that to a leaf and play with it. It can be used for fire, leaves, snowflakes, and more. I'll attach a fire particle .fla that you can tear apart to see the very simple design and compare to the mathematically complex, and very beautiful result.
Best wishes,
Eye for Video
www.cidigitalmedia.com