Some florists will do a sample based on probably the potential budget of the wedding will be. Most good florists will have several pictures on hand of their work and should be able to make a bride very comfortable with their portfolio. It depends on the florist. A florist should be able to recommend what would be appropriate for the color scheme for the bridesmaid's hair. Several flowers have special meanings for weddings.
Ivy symbolizes fertility.
I try to do that all the time. It's very important to know the couple. And know what they like, to produce the perfect wedding for them. The trend right now is more of a stark and simple approach. I think elaborate formal bouquets are sort of out of style, and a lot of people are using big vases of just roses, or greens as you indicated.