S.C.
Ok call me crazy but is it really that big of a deal if "HIS" room is not clean. I mean really that is the only place in the house that is truly his so to speak. I remeber growing up and as long as my mom could shut the door and get to my dresser without triping it was ok. But on the same note any toy or whatever that she had to step over or triped over got removed to the trash. At some point he will be looking for something in his room and won't be able to find it then you can remind him that if his room was clean or atleast picked up he would know where to find his toys and things. Oh and I could't have friends over or go to friends houses unless my room was picked up. It might just be finding the right motivation. Sorry for the rambaling but I hope this helps...