miketv, okay, I can imagine scenarios where the background is most important. Maybe that sort of game would have different themes for the user to go through. In that case, you still don't need to load graphics that are nowhere near where the window the user is viewing. I think that idea to split the single very large image into multiple smaller images would work great. Then, when you only load the images as they are about to appear to the use (and destroy ones that leave), there will be less memory usage, thus a better performance.
When I said the "pseudo-infinite" layouts, I just meant that some game designers have manually created/programmed the level to look a certain way, and every time you play that level it will always look the same. Then, it could be made practically impossible to get to the end, or it could just loop around with more enemies, as an example. A somewhat popular game a while back that I tested was "Robot Unicorn Attack 2". In that game certain levels were always the same, but I never could reach the end.
For the randomized infinite layouts, the Construct 2 start dialog (Ctrl+n) has a great example called "Flying along". Also, the current game/app fad, "Flappy Bird" has an infinite random layout. And, when I say "random" with these games, there are typically restrictions on what can happen so that parts are impossible to complete.