Photo courtesy of Smitten Kitten on Etsy (no longer available for purchase at this time, contact vendor if interested in purchasing)
Sometimes the simple look works best for weddings. This pussy willow bouquet was designed for a flower girl to carry but you could use pussy willows in a bouquet for both brides and bridesmaids alike. If you are DIY'er this shouldn't be too hard to pull off on your own, especially if you have a couple of pussy willow bushes in your backyard! Economical and simple.
Other great natural looks for bouquets include the photos below:
Photo courtesy of The Brass Paperclip Project
Wheat is particularly appropriate since some sources suggest flower girls made their first appearances at weddings in ancient Rome where they carried sheaves of wheat and herbs to ensure blessings of prosperity and fertility.