You are able to customize the title of your WebHelp output by using a custom CSS.
For example, to add a logo image before the title, use the following code:
h1:before {
display:inline;
content:url('../img/myLogoImage.gif');
}
In the example above, myLogoImage.gif is an image file that you place in the [OXYGEN_DIR]\frameworks\dita\DITA-OT\plugins\com.oxygenxml.webhelp\oxygen-webhelp\resources\img directory, thus it is copied automatically by the WebHelp transformation to the output directory.