@
Hudaman - if you need to add multiple images to a book record you could put them into a comic book format (CBZ or CBR) and add that to the book, assuming of course the actual books are not themselves comics.
If the books themselves are CBR or CBZ, then you could put the extra images into a multi-image TIFF and add it to the book, in which case you'll need to set a tweak to make calibre treat the TIFF files as a book format rather than a cover image, viz:
Even though its a bit 'trickier' I prefer the latter; if I see a TIFF format alongside ebook formats (EPUB, PDF, DOCX etc) I know immediately it contains supplementary images, whereas if I saw a CBZ I might wonder if its a comic book version of the actual book.
BR