[SOLVED] How to Make Sidebar Titles An Image

Love this theme! We are working it out and will definitely make a donation! I was wondering how to make the sidebar titles (like blogroll, or site admin, or gallery, or subscribe) as an image.

I saw this site here on the forum and like how she did them. Where would I put the image and what form should it be in? Here's the site I'm trying to emulate!

[url="http://misspickyscolumn.com/"]

Thanks so much!