I think it would be neat if you could make a gallery of images in jpg and similar formats, like, alternate posters, behind the scenes photos, etc, that you could look through, like many dvds and blurays have. You put them all in an extras-subdirectory named, for example, Gallery, like you would featurettes and trailers and all that, and you can click between them as individual images,
There is a somewhat similar request at 'Gallery' extras type, that has been referred to in the past, but that seems to be more about gallery as a video-extra, where my suggestion is directed towards being able to make a custom gallery of image-files.
