Yes! To add multiple images for a book using your BiblioDirect Photo-Email Address, name each email with your book ID number/SKU, then a dash, then the number of the photo:
First photo/ lead photo for your book ID/SKU: 1234
2nd image: 1234-2
3rd image: 1234-3
If you don't put the dash and number at the end, we'll assume that the photo you are sending is the first photo for that book.