Customized Heading on Left NAV - Can I do Image? or BOLD?

I have been asked to find a way to customize Headings under the left NAV.  Temporarily, we are using special characters to seperate them from the rest of the sites under them - It looks horrible.

We have a few group headings on the left nav that act as headings (non-linkable).  We did this to seperate our Left Nav into sections.

I am looking for a way to either bold a Heading in the left nav - Or maybe a way to insert an image graphic into the heading box.  I have tried a few things, and it looks that in most of the places I try to add an image...it's a free-text box (like the by-line in the article pages).

I'm open to ideas.

Thanks,

Matt