So I like to make pixel games but my sprites/background always looks really blurry, which is unfavorable. Can I fix that with maybe an image editor? Sorry if this doesnt apply extremely specifically to snap, i would just like to know if theres something I can do in snap to fix this problem.
Snap's backgrounds and costumes only support non-retina resolutions for UX and resource reasons, sorry. But you should be able to make sufficiently nice onces nonetheless 
you might want to try pixelate effect
I think part of this problem is my fault; long ago I advised Kartik to adjust size of costumes in the costume editor to be as big as possible, thinking that shrinking is easier than growing. But shrinking fuzzes too, partly because of non-integer scale factors and partly because of anti-aliasing.
I've learned not to change size with the editor anymore. I ALWAYS use the "set size" block, because that makes it to where it's not blurry.
If your sprites are made with SVG (vector art) instead of PNG/JPG I think they will also not lose quality.