Turns out all the backgrounds need to be SEAMLESS...Ha ha! I'm new here! I spent about 4 hours designing way cool screens only to see them continue to scroll over and over with weird breaks in the background. I hope I can help someone avoid this fate in the future.
I can't remember any names at the moment, but I do remember seeing programs that can help create seamless patterns for scrolling backgrounds like this, to make sure the ends match up. I remember thinking at the time... that's cool... but at the moment I didn't have any particular use for that kind of functionality. Wish I'd paid more attention now!