$(document).ready(function() {
  $('img.coming-soon').hover(function() {
    id = $(this).attr('rel');
    $(this).attr('src', '/images/brochures/brochure-thumb-'+id+'-coming-soon.png');
  }, function() {
    $(this).attr('src', '/images/brochures/brochure-thumb-'+id+'.png');
  });
});