SOLVED. New question, though: How do I go about making those clouds scroll infinitely? I found two solutions by searching, but it doesn't look like they can apply to what I'm trying to do.
I'm using backgrounds like this:
<img src="http://oi51.tinypic.com/2ijgmro.jpg">
for my Mario & Sonic platformer. In the original Mario World, that background is a single layer that scrolls slower than the foreground, which looks fine, but many of Sonic's backgrounds are multilayered and look much better. So I was thinking of splitting up Mario's backgrounds into layers, but would that add an unnecessary amount to the VRAM?
That background, for example, would logically split into five layers, for each set of mountains and clouds. Is that too much? Most other backgrounds look like they'd work with three or less layers, by the way, so they wouldn't all be this much.
EDIT: And another related question -- what would be an acceptable maximum VRAM each level should have, for those of you who know how large the average Mario level is? Right now it's hovering a bit below 13 mb, and the level, well... barely exists yet. It's only a handful of enemies and some obstacles, only 2500 pixels wide and 1000 tall so far.