<?php

$find = "SELECT * FROM walls ORDER by wallrd DESC";
$run = mysql_query($find);
while ($is = mysql_fetch_assoc($run)){
    $wallid = $is['wallid'];
    $wallfn = $is['wallfn'];
    $walloriginal = $is['walloriginal'];
    $wallcaption = $is['wallcaption'];
    $wallsmall = $is['wallsmall'];
    $wallrd = $is['wallrd'];
    $wallc = $is['wallc'];
    $datelink = date("F Y", strtotime ($wallrd));
    if(!isset($datelinks[$datelink])){
        $datelinks[$datelink] = "<a href='archive.php' title='$wallrd'>$datelink</a><br />";
    }
}
foreach ($datelinks as $row){
    echo $row;
};

// If the above while loop is all you are using the results for, then there is no need for the additional info.
/*
$run = mysql_query("SELECT wallrd FROM walls ORDER BY wallrd DESC");
while($is = mysql_fetch_assoc($run)){
    $wallrd = $is['wallrd'];
    $datelink = date("F Y", strtotime($wallrd));
    if(!isset($datelinks[$datelink])){
        $datelinks[$datelink] = "<a href='archive.php' title='$wallrd'>$datelink</a><br />";
    }
}
foreach($datelinks as $row){
    echo $row;
}
*/
?>