Thanks for the reply twobob. By the time I got done typing that, I looked over and the 'cover' feature was working.
I just dropped the 'black' file in the folder, so I'll see if it gets rid of the white bars.
If this sticks, I'm going to be so pleased. As long as I've had this K3, I've wanted it to show the cover of the book being read. To me, it makes it feel much more like a real book.
Thanks a ton to everyone who has been providing tips in this thread, and mostly to NiLuJe for all your hard work.