When we decorated weddings, my mom always readied a large display arrangement, usually for the entrance, sometimes to flank the head tables, or to punctuate the buffet table. Here are a few examples of big flower arrangements you can use to wow your guests.
Here is one at the entrance of a wedding reception. These flowers were built onto a three-tiered stand, a very heavy one, so its not like someone could just walk off with it. (This is an important attribute; we used to have lots of problems with people taking home our equipment.) This arrangement contains red and white roses, white Hawaiian orchids, and stargazers. My mom wrapped the poles holding up each tier for an extra pop of color — and to hide any imperfections, of course.