I use Inkscape to make maps for a gaming campaign. I started this on what is now my old computer, and this is what I had:

When I got a new computer, I backed up my files and now on my new computer, I am trying to resume my work, but for some reason the image I am using for my background has shrunk, even though I haven't done anything to it.

I don't understand why the picture no longer fills my entire image. Not only am I pretty bad at Inkscape, but I "figured out" how to make my map when I started this, a few years ago, and no longer recall exactly what I did. I do know that the background image is its own layer, as is the grid map.
https://www.dropbox.com/sh/t8q9wy581hpqzjx/AAB-z6GyF2bxhFRAfuiVUOIsa?dl=0 is a link to my Inkscape file on my dropbox.
Any assistance or suggestions would be appreciated.