Welcome to the RetroFE forums
In addition to the code changes, attached is a modified version of the Worlds theme with minimal usage of large sized (size on screen not file size) pictures.As mentioned before large pictures are the primary cause of high GPU usage.Just make a backup of your layouts/Worlds folder and extract the zip on top of it.In the layout.xml file you can find my comments regarding what does what.I've also derived a theme from this for the Arcade1UP cab (5:4 ratio) if anyone is interested.