Instead of using printf() directly you could use sprintf() to put it in a variable first:
$v=sprintf("%s %s %s\n", $myrow["Picture"], $myrow["Date"], $myrow["Story"]);
print(nl2br($v));
But since you're not actually doing any sophisticated formatting, it's probably a lot faster just to use variable interpolation or string catenation and say
print(nl2br("$myrow['Picture'] $myrow['Date'] $myrow['Story']\n"));
or
print(nl2br($myrow['Picture']." ".$myrow['Date']." ".$myrow['Story']."\n"));