Black Calla Lilies
I don't think there are any truly black flowers out there (bummer, right?). But there are ways of dying flowers, or there is always the silk option...in which case color is no problem.
Burgundy Calla Lilies
Fiddleheads (love fiddleheads - the have a decidedly Burtonesque touch to them!)
These could definitely be re-created with some Model Magic or another type of clay and a little finesse - and think of the fun colors you could use! (And by fun, of course, I mean the standard Halloween colors, black, orange, purple...)
Green and Black Sprouts
Black Bacarra (Black Magic) Roses
These roses aren't actually black, but are a deep burgundy with a velvety appearance.
The Best Wedding Flowers
Purple Posies with Fiddleheads
Red Freedom Roses with Black Feathers and Sheer Black Ribbon
If you're looking for a way to avoid flowers in your wedding, there are some fun alternatives out there. For instance, check out this etsy page for some buttony bouquets.
You could also include lanterns as centerpieces, or for your bridesmaids.