I don't know if this would help, but I read a lot of graphic novels, and I prefer CBR over EPUB.
For picture books, you might think about making it a CBR file, they're easy to make and on tablets they're actually easier to read. epub files annoy me because they show very small pictures and in order to zoom you have to double tap and stretch.
CBR files fill the screen on either computer or tablet and while they can be tricky on a regular computer, they zoom and navigate very easily with the nook. Each page fills the screen and when the tablet turns sideways it switches to two pages, like a real book~
stealii, Thank you. This sounds like exactly what I need. Where do I find a program to convert a .pdf to .cbr? I've been finding some online that look like possibilities, but if the site users do not handle the English language too well, I get nervous.