The great designer Bob Gill wrote a book in the mid-80s called Forget All the Rules About Graphic Design: Including the Ones in This Book. My parents gave it to me when they were cleaning out their library (another advantage of being the son of two designers). It's out of print (available used), but a valuable contribution to any designer's bookshelf.

Of all the lessons he teaches in the book, there is one that continually comes to mind. If the message you are communicating is dramatic, loud, dynamic, interesting, bold, etc, then simplify the design elements and let it speak for itself. If the message you are communicating is bland, boring, dull, quiet, etc, then make the design the opposite to pull the viewer into it.

It reminds of a Communication Arts advertising column from many years back entitled "Creative Brats and Creative Adults". I've long lost that particular issue, but there was a great line I'll paraphrase. "A creative adult is one who realizes that an ad about finding the cure for cancer should have a headline that reads 'We've found a cure for cancer' in giant 120 pt Helvetica extra black, all caps".