If your wedding is simple then keep the centrepieces simple. WE had a black and white wedding with punches of fall colors (mostly red) and here's what ours looked like.
We had rectangular tables in a narrow-ish hall so we placed one of these on each end of the table. It was simple, provided light for ambiance, looked good and...best of all... it wasn't expensive. Aquarium gravel and dollar store containers are your friend!!