Having the BG editor in the level settings is really confusing and doesn't make sense.
I think the best would be to add an extra editor, like the Tileset Editor, but for BG's.

Any ideas?

Yeah, I would start it so that you have to import a 512x512 canvas first. That will eliminate a lot of issues right off the bat. So, an obvious message pops up saying "this is not a 512x512 image".

Then I would add the ability to view both the top and bottom images together, and separate. This way we can compare the two. This could also allow the top/bottom half. You will know if it is top or bottom by maintaining a 512x512 image for each.

If it is possible to edit scroll speeds yet, that would be nice. I added more to your old description...Speaking of which I have tried to find a non moving background... But editing scroll speed would be a big addition. We have enough values that it could be added in order of speed from fastest to slowest. As more values are found, we can always add them where they belong.

It would be nice to see the background in the editor as well. I know we have that feature now, but being able to have it reload if possible as the tileset editor does.

I don't know if it is possible to have different backgrounds for every view, but that would be huge too.

You mean to see the BG in the editor? Behind the level you're editing?
That could be possible, but I don't see the point of it.

The other stuff is good ideas, though
And I'm afraid it's not possible to specify backgrounds for each view.