The directory option is a useful way of populating the modules with images either as a stand alone image gallery or as a gallery with images that then can be linked to relevant content.
Content elements available when using the directory option
Naming convention for images
The zentools module has the capacity to create the title, text and link destination elements from the images file name. In order to separate these items you need to follow the following naming convention:
An example file name looks like this:
Resizing files with spaces in the name.
File names with spaces in the them are notoriously problematic to process. The + character is used int he Zentools module to namespace a non breaking space in the module output to get around instances where servers won't process filenames with spaces in the title.
You can see a real live example of how this works on the slideshow demo in the first example which uses the overlay theme or in the screenshot below.