Figured why the heck not. A Valentine to give to your friends.
I think if Sherlock was bored enough, he'd agree to be someone's Valentine. BBC's Sherlock, at least, comes across as asexual to me, so he wouldn't be spending the day with anyone special, though he'd jump at the chance to ruin Watson's plans. XD
Sherlock and John (C) BBC and Sir Doyle
art (C) me
Big Ben photo (C) not me