[KevinH]

Please note epub3 books made of only of images means that images are used in the spine and that is not well supported for many e-reader platforms and there is still debate on how and if they should be allowed. There is also the question of accessibility i.e. where should the alt image description be put for screen reading and accessibility software.

All of this points to using only xhtml files in the spine each loading its own image (either directly or via an svg wrapper) which includes alt info or svg description as required for accessibility as well as other additional information to allow for screen reading of any text or translations.

Most current comic books are in a specialized non-epub format as the epub3 spec has not really been clear.

Even Sigil requires each page to be an xhtml file in the OPF spine to be as conservative as possible and allow their use on any e-reader. These xhtml pages can of course contain a single image or inline svg. That is why most true comic books use their own unique format, not epub.