Vinca,
They turned out great!
I went to the cake decorating aisle of a craft store and found Wilton glitter decorating gel in both white and gold. A squiggle was piped on the top of the squares, then I used a large star tip and piped a pink flower (for Christmas, I made the flower dark pink to suggest a pointsettia). Gold gel went in the center, and a mix of red and pink sugar crystals were sprinkled on top.
These were incredible. Absolutely
delicious! Dense and chocolatey with a raspberry flavor. You can make them now and they will freeze beautifully (undecorated) until Valentine's Day.
May I make another suggestion? Another King Arthur recipe,
Cherry Almond Brownies. These were great, too, and only required a little more effort (dipping them in chocolate). You could use red-and-white decorations on top. Again, they can be frozen for a few weeks (before dipping and decorating).
For both of these, I would strongly recommend lining the baking pan with foil, then coating with cooking spray. I found (because I made multiple batches of both) that you can get much cleaner, even cuts after they've cooled for several hours then are lifted from the pan before cutting.
Good luck, what ever you choose to make!
Oh, and after decorating, the truffle squares kept nicely, wrapped in plastic (after the flower firmed up) for a week. The brownie squares, also wrapped but kept in a cool place (not refrigerated), kept for 10 days. I made it my duty to taste one of these, every other day, to make certain that they were keeping well...