Anchor on CSS list image?

Hey guys.
I have an expandable menu system that uses unorded lists for the menu items (for accessibility purposed). The images for the expandable manu items are little pluses and are supplied via CSS. Right now, to expand the menu, you have to click on the text. I'd like to be able to expand it by clicking on the list item image (the litte plus). Is this possible?

Here's the site:
URL
so you can see what I mean.

Thanks.