So I ordered about $400 worth of silk flowers from http://www.silkflowersfactory.com/ which I am waiting to come in the mail. I also ordered more styrofoam balls on ebay. Some of them are 5" which will be used for the main centerpieces and then the others are 3.5" which will be used for decoration all over the tables. I got them from http://stores.ebay.com/seasonaldecorator. I definitely recommend them. They ship very quickly and they will combine shipping costs if you buy more than one thing at a time. The prices are also very reasonable. If you are making poms, the styrofoam ball is probably the most expensive part of the entire thing and I did the math and even with 1/2 off coupons from Joanns or Michaels, this is still cheaper (even with shipping costs).
Along with the poms for the ceremony and the centerpieces, I was thinking of possibly doing something like this to decorate the cake tables and escort tables:
For the actual centerpieces, I am hoping to do something similar to these: