Using a different mix of greenery is what makes your larger designs interesting. I have seen brides skip the flowers and just use cool greenery to decorate their ceremony venue with.
Variegated pittosporum has a heavier stem with oval, waxy leaves.
It lends itself well to cutting apart and using the smaller pieces to fill in the center of the church floral.
Use a branch cutter or floral snips to cut the heavier branch quickly and easily.
I place smaller cuts of greens in the center of the floral design.
Stagger the height of the different stems of the pittosporum.
Note that the variegated pittosporum has a white edging pattern on the sides of it's leaves.
The design is beginning to take a shape. Remember this doesn't have to be totally packed with greenery because you will still be adding leather leaf fern and flowers.
The final goal, however, is to hide your mechanics (in this case - the green foam).