That's indeed very weird. For me in IE7 no list images show up at all. I can't think of a proper solution for this problem. Maybe you should try this, this is just a guess, it will probably won't work either.
Code:
#left ul {
width: 200px;
padding: 0;
margin: 0;
margin-left: 30px;
list-style-image: url(images/list_icon.gif);
}
#left ul li {
padding: 4px 0 3px 10px;
margin: 0;
border-bottom: 1px solid #192127;
list-style-image: url(images/list_icon.gif);
}
I just copied the list-style-image command and inserted it also in the declaration for #left ul li. Try this, I have no idea if it will work but it could.