I was able to do this successfully. Only inaccuracy in the instructions above are that you cannot designate "hidden" under the customization. If you leave the placement as "right," for example, the image will be replaced by your image as described above. If you designate "hidden," nothing appears. (Note: your image should be 182x49; otherwise modify the style code accordingly.) Here is my implementation with the company name removed:
<!--GET SATISFACTION WIDGET-->
a#fdbk_tab {background-image:url("http://dev.xxxxxx.com/images/test_wid...; height:182px; width:49px;}
<!--END GET SATISFACTION WIDGET-->
<!--GET SATISFACTION WIDGET-->
a#fdbk_tab {background-image:url("http://dev.xxxxxx.com/images/test_wid...; height:182px; width:49px;}
<!--END GET SATISFACTION WIDGET-->