@rsaurer Hmm, alright. That shouldn't be a problem to implement, though I'm not sure why it wouldn't just use the default available. I've added it in to force the default that I used when I designed it. Hope it works now!
Try the official image from the RetroPie website. Custom images are not supported here. If you have an issue with the official image we'll be glad to help. If you're using one from another source, contact who created that image for assistance.
I've had pretty good luck using Emulation Station to scrape the games and folders. Below is a working example for the original 'Duke Nukem' that illustrates both.
<desc>Set in the year 1997, your mission is to stop Dr. Proton, a madman bent on ruling the world with his army of Techbots. As the irrepressible hero Duke Nukem, you'll chase Dr. Proton deep into the Earth, then to his lunar space station, and eventually into the Earth's nuclear ravished future.</desc>