My college kid is arriving home for a visit, which is why I'm going to bail on you guys today. So that your stop here was not entirely wasted:
Kuriositas (one of my favorite blogs to visit for visual inspiration) has an excellent post here about selective color photography.
I gave it a try, and my first attempt came out rather romantic:
To get the effect, I selected every part of the photograph around the rosebud (you can see the original here), and then selected the black and white effect to alter the color (I use Microsoft Photo-It, which is no longer sold, but I think most basic photo programs have this sort of option.) For those of you who are making your own covers, this could be an interesting way to bring out one element of a photo or image you're using as your art.