Whenever I need to do something like that, I like to use CSS.
I would go into the index.php file and, f'rinstance:
<div id="gallerytitle">
<h2 class="title"><span>Gallery title</span></h2>
And in the css,:
div#gallerytitle h2.title {
background-image: url(mygraphic.gif);
background-repeat: no-repeat;
width: 285px; /* need to have enough room to show it - matches size of graphic */
height: 46px; /* need to have enough room to show it - matches size of graphic */
/*then, hide the ugly text, but preserve it's content for search engines */
#gallerytitle h2 span {
display:none;
}
Just a simple CSS image substitution thing, but easy to use and search-engine friendly.
HTH!