My suggestion is to modify one of the existing character sprites - its easier than creating something from scratch, and will be consistant with the existing style of the other characters.
Right now, Terrence's main distinctions are green shirts and trousers (a jumpsuit I'm assuming), black shoes and blonde spiky hair. Shouldn't be too hard to modify the current Davy sprite for that, I'll see what I can do. Were there any other parts of his appearence/characteristics you'd thought of?