We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Apple's eBook Image Restrictions
EBook Image Restrictions
Apple will not accept ePUB files containing individual images greater than 4 million pixels. Authors intending to sell their eBooks on the iBookstore should confirm that images included in their ePUB file comply with this requirement.
If you use the Lulu EPUB conversion tool, we will automatically resize image files, including your marketing image, during conversion to meet this requirement.
TIP: How can you determine if your images are in compliance? Select the image in your file and view the image properties. The image size will display as dimensions. For example, if the image size is 900 x 900, multiply the numbers to determine the total number of pixels. In this case the image consists of 810,000 pixels.
If any image within your file exceeds the 2 million pixel limit that you wish to manually resize, open the image in your image editing program, resize it to meet the requirements, and replace the oversized image with the newly resized image.
Attention InDesign Users
If you create your ePub files using InDesign, an OEBPS/Images/191.png file is automatically created. The Lulu Distribution Team has seen significant numbers of eBook rejections from Apple based on the size of this file.
In order to speed acceptance of your eBook into the iBookstore, we recommend you locate this image file, confirm its dimensions comply with Apple's requirements, and update it if necessary.