[Dave]

Made a jQuery script for fun which should download any images in threads.
Open up developer tools and execute the following in the console:

$(".postcontent img").each(function(index, val){
   if($(val).attr('src').indexOf("smilie") === -1){
      var a = $("<a>").attr("href", $(val).attr('src')).attr("download", $(val).attr('src').split("/")[$(val).attr('src').split("/").length - 1]).appendTo("body");
      a[0].click();
      a.remove();
   }
});

Will probably download duplicates as well, but you get the idea. It'll only download embedded images.