Well, maybe the term "hidden messages" is a bit of an exaggeration but I'm sure you're familiar with the genre: logos that exploit the use of negative space or other optical tricks to add a little something to what's evident at first glance. Collections of such logos are far from new but British plastic business card printer Oomph! recently cooked up a nicely-done graphic that included the usual suspects, as well as few obscure ones I wasn't familiar with.
And just for fun I've added a personal favorite that wasn't included, the notorious 2008 rebrand for the France Tourism Development Agency. The one below left is a classic take on Marianne, the national emblem of the Republic of France. If you're not familiar with Marianne, there she is at right in Eugène Delacroix's mythic Liberty Leading the People, where she's pictured during the French Revolution. Half naked, you'll note.
So you can't blame the designers of the France Tourism logo for following in this tradition. The only problem is that the designers apparently forgot to point this out to their client. So the new logo was launched with great fanfare, only to be hastily withdrawn when someone pointed out its racy nature. While this reaction is perhaps understandable, the revised logo at right somehow seems bland in comparison.