Easy as pie to create, too... just put a blob of polish on your surface of choice, and grab a toothpick.
A pair of dots side-by-side give you the rounded top of a heart, then just drag the tip of your toothpick down through the polish to make the pointy base.
From there, your options are almost endless. One single heart on the corner of a pinky? One great big lace-edged expression of love? Or even just a montage of little guys in all the shades of pink vying for center stage. I'm going to try and get at least three Valentine's-themed manicures posted in time to provide ideas for your perfect holiday look :)