Themes

um, this is untested but you could try

.categoryname {
background: url(/images/icon.gif) 2px 50% no-repeat;
padding: 0.5em 2.5em;
}

where /images/icon.gif is the path to and the filename of your icon.

you may have to adjust the padding to suit

and also I haven't tested if class="categoryname" is used elsewhere, so that changing the style will change it in those place too

cheers