We have a rule about the girls' bedrooms. They have to clean it once a week.
We used to be easier going on the girls when it came to their rooms. We would tell them that their bedrooms were their own space and that if they were going to keep them messy then they at least had to keep the doors closed. That changed however, after we began having unidentified smells lurking outside of their bedroom doors.
As of recently Jasmine has actually begun enjoying the once a week cleaning. She wont admit to it. She'll even go as far as to complain when I say, "okay, it's time to clean your room." As I think most children do.
Each week she goes in and tears it up even more than it was to begin with. Some weeks she will have her walls covered in posters, pictures and drawings and others she'll have them completely clean. Some weeks she move her bed around and others everything gets rearranged but it seems like every time she has finished she is happy and she likes what she has done with her space. Which just proves that making your children clean doesn't hurt them. :)