Ask Gomez and Morticia; black can be a very romantic color. Whether you decide to go full-on black dress and matching veil or you just want a touch of the dark aesthetic in your special day, you'll be wanting as many spooky/gothic/Halloween/Autumn flower ideas as you can get your hands on.
For this moment, there's the new Bridal Bouquet Builder Pinterest Board and a short post on the ways you can add variety to your dark bouquet.
Handles are always a fun way to add expression to a bouquet. I've seen a lot of brides in this "theme" using hoop bouquets rather than handled bouquets, but I've also seen Tim Burton fans use black and white ribbons to theme their bouquet handles. Additionally, a more Gothic bride may find it intriguing to add a collar of black lace or ribbon around the base of their bouquet. Play with ideas and search around the internet for more ideas!
From skull vases for your centerpieces to small charms in the thick of your bouquet, accents can make bold statements in your bouquet. In fact, some brides will have a bouquet entirely made of ribbon and accent charms. The sky's the limit. Charms are a popular way for Tim Burton fans to show their fandom in their bouquet, if a quick Pinterest search can be trusted for such things.
A Splash of Color
Sometimes, a block of black flowers can blend into itself and turn out less stunning than you imagined, especially if you're wearing a black dress that the flowers might camouflage against! Try adding a splash of color, such as a sultry red rose or a small pop of white baby's breath to take your dark bouquet from "okay" to "WOW!"
For The Not-Quite-Black-Flowers Bride: Try Dried Flowers
Dried flowers tend to have delicate and muted tones that can be very effective in weddings that have a darker theme. For brides who don't feel a straight-up Gothic wedding is for them, a more centrist alternative is dried flowers.
Pro Tip: When looking on social media for dark/gothic/spooky wedding ideas, use the word "moody" in your search.