This question:
Comand: "unity-control-center background" not working
got an answer, simply just this:
unity-control-center appearance
Well, it works perfectly. I've tested it and I voted it up. When I came back to edit it. Ooops gone!
I agree that it should be flagged as low quality, But I do not with removing it. Now, the question has no answer and any one comes later cannot know that there was a working solution.
I think it will be helpful if it is left as a comment at least. Or could we have some thing like HOLD period similar to questions.