OSC REPLIES:
Alas, I barely visualize at all. I have sketchy maps and the odd scene here and there, but what goes on in my head when writing is mostly the sense of what a community is and how a person fits into it. Everything is maps; scenes are few and far between, and only when I need to describe something in order to help the reader understand what's happening. I have description or visualization for its own sake. I don't even remember my dreams ...
As to the cover art for the Ender books, they are chosen entirely by the publisher's staff, and while I have liked many of the covers TOR and others have created for my books, the Ender series covers are not among the ones I liked. Indeed, I still don't understand why anyone who would like a book of mine would ever pick up something with a cover like that. But ... in this as in all things, the publisher knows best