The illustrations themselves are all okay, as far as I can tell; I've tried to make sure that they have enough contrast even on a greyscale screen like the Kindle's. However, there are some formatting issues with a few of the pictures on the regular-sized Kindle's screen. I'm not sure if these issues also appear on the DX. They might not, because they seem to occur due to the Kindle's small screen width.
I'll talk to my publisher to see if we can get these problems fixed.