There was a lot of anger over how Iga (director/producer/some sort of bigwig for the Castlevania series) talked endlessly about how the PS2 incarnations are more important to him than the DS versions, hence why the switch in art style. Apparently he felt that Ayami had to focus on those, and that dividing her attention would utterly destroy the pantheon that is a third dimension Castlevania (....right....). He also spoke at length about how the anime style "should draw in more kids" and that is how he felt it would work best on the DS.
Nevermind that there's blood spurts, some heinous enemies, and suggestive artwork (given some of the female enemies), and the overall feeling that Castlevania embodies a deeply Gothic theme that all gamers resonate to and have since their inception in the 1980s.
Iga, of course, really only came onto the scene with C:SOTN, and despite that it is a masterpiece of gaming, he's pretty overrated, and has been making some questionable decisions with the license. The switch from the Gothic/Victorian style for the DS game is a travesty in my opinion, as I think it was not warranted and that another design crew could have easily come in and replicated something similar to Ayami's work, rather than the bastard abortion we have now.
But I'll still buy it. Meh.
As for the old box art, yea, those were great. I like the gritty, somewhat Renaissance inspired artwork. I also like the story of Nintendo Power putting Simon Belmont holding Dracula's head on their cover, driving people to angrily write in about their kids having nightmares. Classic.
On to the box arts....
1) That particular stance is used over and over in anime, just like how all sorts of things are copied endlessly in anime.
2) There is a discussion at PGC.com right now about how there seems to be a subliminal message to the DS boxart. You'll notice a lot, a lot, employ the use of characters with their hand stretched out, usually in a fore-shortened sense, as if they are trying to touch the player. Pretty interesting. Trauma Center, Castlevania, Trace Memory, Phoenix Wright, ...even to an extent things like Yu-Gi-Oh and Frogger. I bet someone at Nintendo is telling people to think about cover art with an emphasis on hands/touching/etc.