Want to remove the tab images from my sub-nav - html

Question

I have a django app that has a horizontal nav. The horizontal nav looks like the image below.
Now what I want to do is edit the sub navigation for storage orders. For both Delivery and collection orders tabs, I want both of these curved tab images removed, and have both of these tab in a retangular background color similar to my tabs. Something like this.
base_menu.html
<ul id="toc">
<li id="current"><span>Home</span></li>
<li><span>Create quote/order</span></li>
<li><span> Item Search</span></li>
<li><span>Storage orders</span><br/>
<ul class="subnav">
<li><span>Delivery orders</span></li><br/>
<li><span>Collection orders</span></li>
</ul>
</li>
<li><span>Delivery list</span></li>
<li><span>Collection list</span></li>
<li><span>Export for invoicing</span></li>
<li><span>Backup data</span></li>
<li><span>Help</span></li>
</ul>
<br/>
base.css
ul#toc {
height: 2em;
list-style: none;
margin-left: 20px;
padding: 0;
position relative;
}
ul#toc li{
background:#ffffff url(../images/tab.png);
float: left;
margin: 0 1px 0 0;
}
ul#toc span {
background: url(../images/tab.png) 100% 0;
display: block;
line-height: 2em;
padding-right: 10px;
}
ul#toc a {
color: #000000;
height: 2em;
float: left;
text-decoration: none;
padding-left: 10px;
}
ul#toc a:hover {
background: url(../images/tab2.png);
text-decoration: underline;
}
ul#toc a:hover span{
background: url(../images/tab2.png) 100% 0;
}
ul.subnav {
float:left;
display:none;
position:absolute;
margin-top:10px;
z-index:999;
padding-top:2px;
}
ul#toc li:hover .subnav {
display:block;
}
Update #Yule I have done what you said, but nothing changes. I have instead wrote.
ul.subnav a {
background: url(../images/squaretab.png)
}
And this gives me this.
Now here U have a grey image on the left, but only partially. I need to remove that green tab completely. How would I do this?

Answer 1

Just set a BG image on subnav li:
ul.subnav li{
background: #ffffff url(../images/squaretab.png) no-repeat;
}
ul.subnav li a{
background: none;
}