Background size?

I’m using one that is 1350 and it works fine for my site but I am concerned that it will screw up with larger screens. Looks terrible in the resolution simulators. https://indiearchives.com/

The background dimensions are as wide as your user’s browsers – we can’t answer this, go with what’s on your Google analytics.

I put this code in the theme options section for custom css:
body {
background-position: top center;
background-repeat: repeat-y;
}
So now the site will appear basically as I see it even on larger resolutions, and still remains responsive to smaller resolutions.

Put a link up to your site if you still need help.