They are all modeled in the IMVU 3D Chat software (which is like Second Life, only invented first and envisioned as a chat program rather than a true virtual world), using items available for purchase in the avatar catalog.
I do try to adapt the characters faithfully, and if an exact copy isn't possible, I do try to capture the style, personality, and essence of the character as best I can with what I've got.
It takes a lot of money to afford every character I've played (usually $10-$20 per character), and hunting the right items in the catalog for me tends to be SERIOUS BUSINESS. I don't give up until I find what I'm looking for.
I've been a member of the service since 2007, and to date I've played about 55 characters, but only a few of them are actual Castlevania characters, and I'm posting them here.