Meanwhile I continued my JQA adventures with the FolderGallery. Works very well, basically. Only ColorBox did not work well with IE, so I tried Slimbox. Slimbox looks good everywhere, but I cannot browse the images in the gallery. Apparently that's because the rel attribute contains 'lightbox' only, while it should contain a group name, too.
How do I get the group name in there? (I already went through the source code but couldn't find it ...)