Hello!
After following the advice here to have one image for desktop screens and a different image for mobile screens, the quality of my banner has very noticeably downsized. I’ve made sure to try re-uploading the image in different resolutions, yet the problem persists. (I’ve now gone back to the original high-resolution version of the background)
For a visual reference, here’s the original image:
And, here’s a screenshot of it from my page:
I searched for solutions to this issue, and found this. However, either there is a difference between the banner codes of Dawn and Refresh, or there have been changes to it, as I cannot find the sections in question within the image-banner.liquid file.
I’m not quite confident enough in my.. very lackluster coding skills to go experimenting around by myself, so I was wondering if anyone could help me here! 
Thank you in advance!