Thank you, works like a dream - although I changed the operator to >= otherwise any date that's exactly x months in advance didn't show any image at all. I also changed it to days instead of months so that I could be more accurate, i.e.:
<?php if((date("Y-m-d", strtotime($row_WADAclients['StagingDate'])) >= date("Y-m-d", strtotime("+31 days"))) && (date("Y-m-d", strtotime($row_WADAclients['StagingDate'])) < date("Y-m-d", strtotime("+60 days")))) { // Show if column... ?>
Thanks again!