photo display for a party - double sided so they can spin a little. / you could do these right beside the hanging table. Maybe use streamers in your colors to hang from the exposed trusses to kind of add color and a block from the big empty space.
Create an inexpensive and easy centerpiece using food coloring and simple white flowers in bud vases. I like the idea of the colored water with maybe white roses and the colors of the water would be the colors of the wedding