First of all, what a gorgeous pic! The table and chairs are great! Is that your setting too?
For my BF wedding, we made simple, inexpensive, and IMO beautiful centerpieces using limes.
We used two glass, cylinder vases: one skinnier one to fit the size of the stems, and one larger one for the limes.
We put the smaller cylinder inside the larger cylinder (you could use whatever shape you like), then cut up about 4-5 limes in a mixture of slices and wedges and arranged in between the inner and outer cylinder, and submerged in water. Then we placed a stem of hydrangea in the inner vase, and tied with a pink bow.
Maybe you could use a few callas and brown bow instead. We added a few candles and vióla...
She purchased the vases at Hobby Lobby for super cheap, and limes were about $10 for a case of 100 (and I would think available pretty much anywhere).
The limes looked great...fresh, fun, and green! As an added bonus, your guests could "borrow" a few for their Coronas