I was wondering the same thing myself. Here’s how I did it: The first thing I had to figure out was the div id to work with, in this case, it is called ngg-webslice and located in the file called nextgen-gallery/widgets/widgets.php. You’ll need to edit the file around line 393, it looks like this:
$before_title = "\n" . '<div class="hslice" id="ngg-webslice" >' . "\n";
$before_title .= '<h2 class="widgettitle entry-title">';
$after_title = '</h2>';
$after_widget = '</div>'."\n" . $after_widget;
You’ll need to remove both h2 from the code above, so your code will look like this:
$before_title = "\n" . '<div class="hslice" id="ngg-webslice" >' . "\n";
$before_title .= '<class="widgettitle entry-title">';
$after_title = '';
$after_widget = '</div>'."\n" . $after_widget;
Then you’ll need to create a new entry in your main css file that looks like this (change the font and size to whatever may suit your needs:
/*Entry below fixes the font on the picture widget */
#ngg-webslice {
font-size: 14px;
}
Please remember, if you upgrade the plugin you’ll most likely have to redo the changes to plugins/nextgen-gallery/widgets/widgets.php