Above were only a few examples -- of course I try not to expect to much of them because they are still so very young but sometimes I wonder, if I expected more, I would get a better result???
I believe, in general, fights over the messy status of kids rooms are battles that are not worth putting much effort into. Outside of keeping it relatively clean so as not to have her spend a lot of time in a dusty(any allergy problems?) environment, I tend to say let the kids have control over their own little piece of the house, they have physical control of nothing else-you do.
I am a believer in kids understanding and receiving the natural consequences of their behavior. I am also a believer in the notion that kids have "goals" attached to their misbehavior and that if you can figure out why the child wants to get the responses she gets from you for her misbehavior then you are on your way to some solutions. For the best introduction to these parenting philosophies and some practical suggestions on implementing them, I strongly suggest buying The Parent's Handbook by Dinkmeyer and McKay. I recommend very few "parenting expert" books but this is one of a very few that all parents would benefit from.