There's been a lot of people flagging images that are still in the mod queue lately. The flagging page says a good deal about what you should flag, but little about what you shouldn't, so I think a line saying not to flag unapproved posts should be added. Preferably near the top and in bold so people notice it more easily.
Of course, a more permanent solution would be to disable the ability to flag unapproved posts in the first place but this should serve as a good deterrent.
Updated by Log