They layout should be ideal to comfortably read on PC & tablet. I don't plan on making a phone-friendly EPUB due to all the inline artwork getting messed up. I read EPUBs with images and it would look more like 'Huckleberry Finn'—one big image per page—and it would reduce its overall quality with a simplified layout.
White Background:
If there's more demand for a bright-white background version (for whatever reason) I might consider adding such a perverted edition (other's can comment here). Though, I had never imagined there was a demand for it as I personally very much dislike reading on white-background.