If you need to, you can manually create CBZ comic book archives, simply by renaming all the JPEG files you want to put in to the book in a 001, 002, 003 etc. sequence and compress it using any file manager with ZIP support. After that, just rename zip to cbz and that's it. You can even find programs that can automate and speedup the creation of these comicbooks.
Open JPG file Open CBZ file