Just my opinion-
Let me start off by saying that I love all things dark- from clothing to music, and it pervades through my favorite tarot decks as well. Now, by dark things, I don't mean gothic. I attribute a lot of the dark decks to be this strange fantasy goth inspired artwork that just emanates a level of inexperience and a sense of child like gore. Its just not the kind of dark that I prefer to play with.
I would suggest the Hermetic Tarot. It is all black and white and is marvelously deep and full of symbolism. I couldn't recommend any other deck but one that would help you learn more about the tarot.
There is the Wild Unknown Tarot. It deals with dark themes with beautiful artwork- and it helps bring the darkness through it's rather sketchy and neurotic artwork.
As stated about I would also look at the Mary-el. The deck is fantastic for meditation, or for cutting the boarders off and using as artwork on things that you cherish. If I ever lose a few cards from a deck I use the rest of the deck as artwork or bookmarks. I have even written my contact information down on own of these now miscellaneous cards.
Finally, I would recommend the Thoth deck. This is my daily deck and I love its darkness and how steeped in history the deck is.
Good luck on finding the perfect one for you!