Your images should be 150-300dpi resolution - or they may seem pixilated in printing.
Full page with Bleed Custom Covers and must be sized at 6"x9" with 4.75"x7.75" active content or 1800 x 2700 pixels
Dividers must be sized at 5.75"x8.75" with 4.75"x7.75" active content or 1725 x 2625 pixels
Full page non-bleed Dividers and other images must be sized at 5.5"x8.5" with 4.75"x7.75" active content or 1650 x 2550 pixels
For other images to upload, size your image to a maximum of:
Full Page: 1650w or 2550h
75%: 1237w or 1912h
50%: 825w or 1275h
You may have to try different size options on your picture for best look. Choose a smaller option at first, 25-40%. Save and then view your book.
Also, do NOT upload files of the following type -- they will not work: .doc, .pps, .ppt, .txt, .html