with custom css styling in your template you can add a different background image to it. I realise it isn't perfect but if you can make the menu image background transparent, then you can add another image behind it to highlight it like this:
| Code: |
.moduletable_top img:hover, .moduletable_top #current img{
display:inline;
text-align:center;
background:url(images/highlight.jpg) no-repeat;
}
|
this code will make the active menu item AND items hovered over display another image behind them which you can use to highlight the active/hovered item
(please note that the module has the _top suffix applied in this case)
hope this helps