Humm I think it is hard to work in a BG after you have done the piece personally, but I would say some thing dark or neutral maybe like a Victorian picture frame and tie in more of your theme of clocks?
Either way I like the piece as it is now, Oekaki and I never could get lines like that >>;;;
Honestly He looks like he's about to pull some sort of evil but entertaining trick. Maybe a curtain background, as if he was on a stage. Not that I dislike anything Victorian, just trying to give you some variety!