Read up on *nix timestamps. Once you understand this, it should be easy to create logic for the proper image. Figure out the timestamp for Feb 11 and today's timestamp, then compare them. Ultimately it would look something like this.
<?php
$todays_date = time();
$feb_11 = mktime(0,0,0,3,11,2003);
if ($todays_date == $feb_11) {
$image = "heart.jpg";
} else {
$image = "something_else.jpg";
}
echo "<IMG SRC='$image'>";
Check this, I didn't test it, not sure of the syntax of mktime.
