Buy a bunch of different tiny gourds and pumpkins at the supermarket and get some orange and green vining floral pieces. Or you could scatter the gourds along the middle of the table with votive candles mixed in. Find clear glass pieces to put the candles in at your local thrift shop. You may even check the Thrifts for the autumn floral decor.
You could put a metal bucket of German beers on the tables. People who like to drink their beer warm as the Germans do could even drink them.. Maybe little German dolls in leatherhosens.
I would suggest blue and white Bavarian check table covers and table decorations. You should be able to pick some up at a store that sells Oktoberfest party decorations.