As soon as you say "8x10", I have to ask "Is that really an e-book?" An e-book doesn't have a particular page size. The e-reader screen is however big it is, and the e-reader will reformat your pages to fit the screen.
Also, most NOOK owners still have the E-Ink NOOK models, which can't render color at all and do a poor job of rendering pictures at all.
The NOOK screen is 800x600 and the NOOKcolor is 1024x600, so that's all the detail you need in your images. I suspect yours are far more detailed than that, and all of that extra detail will be lost on an e-reader.
If your are formatting like an actual print book, forget it! Take out all your extra spacing, do not have gaps between paragraphs. And keep your skipped lines to a minimum. No headers! No page numbers, etc. Keep that book as compact as possible. One page should flow to the next with no spaces...I do everything I can to compact mine down. And I have over three hundred page books in ebooks with no problem. Hope this helps!
Did you ever find an answer to this question?
I have several books by authors who write detailed how-to books, sometimes with more than 400 images in them, rounding their size sometimes to 30MB or more. The ebooks format just wonderfully, and are accepted at every major distributor (Apple, Amazon, Kobo, Sony, etc.) without hassle, but not Barnes & Noble.
I've not only called several times, but I've emailed the exact same question more than ten times to support, and have never had any sort of response (I've found B&N's support to be horrendous, maybe the worst of all the distributors--and that's saying a lot).
Any help greatly appreciated.
Use Openoffice writer to export your ebook in a PDF file. While saving a box will come up : Under "General" /"Images" click the box marked "Image Resolution" and click on either "75 , 150, 300. 600 DPI"
Your pictures will still remain the corect size but the pixel count will change. This will make your finished
PDF file much small. My ebook was over 140mb and after setting the DPI it went down to 11mb.
Hope this helps.