The font name to be used to generate the image. The font name will be matched with @fonts[FONT NAME] to determine the font file to use.
If FLIRStyle.inheritStyle is set the CSS font will be used. This means you can use a style like <h1 style="font-family: 'Custom Decorative Font', Arial, Helvetica, sans-serif;"></h1> and have it work. But if images are off or FLIR is disabled the Arial will be used.