[JSWolf]

You cannot rotate the images based on the orientation of the device. There is no way to tell what the orientation is. So the best way to do your book is to set it up as best you can for portrait.

Now given that devices like the Kobo Aura HD, Kobo Aura H2O, Kindle Voyage, Microsoft Surface tablets, and other devices, you do want to use high resolution images. 1440 lines would do well enough if you can go that high. Yes, I know this is going to make your eBook huge, but in order to look it's best, you have to not skimp on image quality.