I have written a 'scroll/image roll' package that could be considered an extension to image-mode.
The package provides a 'displaying' mechanism for displaying images/documents as a single 'virtual scroll'. The main feature/advantage of the package is that it allows for the 'much requested' continuous scrolling.
In the package I have extracted (and improved) the 'display engine' (or whatever to call it), from some earlier experiments of implementing continuous scroll into doc-view and pdf-tools.
The current package can be used for displaying documents like books, but also for displaying a selection of images. I first thought of calling it papyrus.el (because scroll and bookroll, would clutter too much the Emacs namespaces), but finally I thought, as it can be used to show images on a toll, and can be considered an extension to image-mode, it would be better to call it image-roll.el (or maybe just roll), opinions and suggestions about the name are very welcome.
For testing, he package contains a `papyrus-demo` function that can simply be called after loading the package (best after starting from emacs -Q).
Additionally, as a final step, and as an example of how the package can be used, I have included an `image-roll-directory` function in the last section (of 38 lines only) in the file, to provide an example of how the package can be used to display all images within some directory on a 'roll'.
This is only a minimal example; as this does not have my priority, I did not bother to make it 'fit/scale' the images.
However, I have written also an extension for `pdf-tools`, that provides a toggle function so that users can toggle between the 'single' page displaying, or the `image-roll` displaying. That file can be found
here. That file can simply be downloaded and loaded (after first setting the path to image-roll.el at the top of the file, of course this requires pdf-tools to be installed).
I would be happy with any feedback, and info about if and how (what is required) this could be added to Emacs core. If you think this package is not a good candidate for core (after the required modifications), then I would also be happy if it could be added to ELPA (although the package on itself is not very interesting, it should get used by 'extensions' e.g. for pdf-tools, dired, doc-view, djvu.el etc.).