The backgrounds come from different Castlevania series, some have been reworked for the game.
You can find:
Big Bridge : Super Castlevania IV, the bridge leading you to Dracula's Room.
Burning Village : Vampire's Kiss (Dracula X), village of the 1st stage.
Castle Entrance : Castlevania's very first background!
Castle Ruins : Castlevania II, Simon's Quest, Dracula's Castle in ruins.
Castle Treasury : Harmony of Dissonance, Corridor leading you to Dracula Wraith's Room.
Chapel Tower : Circle of the Moon.
Clock Tower : Castlevania Legends, Game Boy version reworked for the game.
Death Tower : The Adventure, symbolic Game Boy level reworked for the game.
Dracula's Room : Symphony of the Night, the famous Dracula's Room.
Gallery : Portrait of Ruin, even if it's similar to the room with the 5 portraits, this gallery is a fictive background made for the game.
Lost Village : Dawn of Sorrow, more exactly, it is the forest surrounding the village.
Mad Forest : Dracula's Curse, one of the first forests of the game, also the place where Sypha is prisoned.
Plant Castle : Belmont's Revenge, one of the 4 castles (with the Rock Castle, Sky Castle and the Crystal Castle), this background has also been reworked for the game.
Romania Castle : Bloodlines (New Generation) 1st stage of the game.
The Study : Aria of Sorrow.
Village Ruins : Rondo of Blood, 1st stage of the game, also known as the "Dinner of Flames"
Wygol Village : Order of Ecclesia, main village of the game.
And a picture featuring some of them: