Who do i talk to, to discuss a stickpage competition with?
other than stone and CJ

There is no one else.

They are literally the only members of the Stickpage Events Bureau

Of course, if you would like to host a competition yourself you are more than welcome to do so. It's what the Animation Attack section is for. You'd have to provide your own prize though, and you wouldn't be able to automatically get the winner up on the Stickpage front page or anything.