The Scratch Animators of Cartoon Fight Club!
Fox: Hey so, you can actually do a scrolling background in scratch, it's simple, sprites can only be as big as the screen, however, if it is in a dot costume, it can be made much bigger, and then changed into your original background, something like this
"When green flag clicked
change costume to "dot"
set size to 800%
change costume to "background""
From there you can move your background and keep it bigger than the screen, I did this in Dark Sonic vs Don Patch