With the portlet Image album you can select a folder with images to display in a slide show. The slide show can start automatically, through a link "Play" or you can click the numbering beneath the image.
One folder - one slide show
If you have several slide shows you can also select a folder containing several folders. Then there will be a thumbnail with the first image in the folder and information about how many images the folder contain. When you click a thumbnail there will be the same view as in the image above.
One folder with subfolders - thumbnails
Permission rights! This portlet/function requires a license for Image album.