I could see a Castlevania anime done in the art-style of Vampire Hunter D: Bloodlust. Carmilla's castle is gorgeously over the top and gothic, right up Castlevania's street. The beautiful art style, with a mix of beautiful men at times (D, Meier), and grotesque monsters would fit well with taking inspiration from Ayami Kojima's designs. I'd like to see either a movie, or a tv series. Something based on CV3 could work nicely, as it's got a good range of main characters, or Lament of Innocence (it would be interesting to see a prelude to Sara being kidnapped). Lords of Shadow, with the modern parts of LoS2 tweaked, and the gaps in between MoF and 2, would also work really nicely. Definitely dark, and mature in tone I'd say, beautiful and gothic, and not afraid of gore in the right places. I suppose that a live-action version could also work well, but the cg and physical sfx for the monsters, and environments, could be tricky to pull off well without a really good budget.