I ran a non profit teaching kids to code and this was one of our projects. I am hoping to get a bit more active in the community here. Love the forum and project sharing. I saw a post on a closed thread recently about parallax scrolling and Snap!. I uploaded one of our projects where we did just that
https://cloud.snap.berkeley.edu/project?user=nedens&project=Flappy%20Dragon
There are some custom blocks that handle some of the heavy lifting if I remember correctly. Looking through the forums I found some better ways of possibly handling some of the layering. As an aside it would be really great to be able to just put something on a layer and have it stay there (not dependent on when a sprite is created as new sprites used to at least appear on top).
Anyway I'll leave this here in case it helps someone work through the idea of parallax scrolling backgrounds in Snap! as it is completely possible.