Our wedding is Oct. 29th. I got great ideas by just typing in fall weddings, fall wedding centerpieces in yahoo image web search. We are using lots of pumpkins! Good luck!
I went to a wedding in October 2010 where they used gourds, leaves, and pinecones. It really looked great.. even though it doesnt sound like it lol.
I found a a lot of pictures on the www.weddingfavorstolove.com Blog for Summer and Fall colors. Here is the link: http://weddingfavorstolove.com/WeddingBlog/?p=53
I think this maybe a good start for what you are looking for.
Click on each tool to see a sample.