Formatting images to be used as wallpaper on mobile

Site URL: https://www.aboydandhisblog.com

(Note: site is not yet live)

I'm creating a site to advertise my services as a freelance writer, but because I have a background in photography and thousands of beautiful pictures from around the world, my site is going to be more visual than most. Part of this vision involves the use of highly specific background images. 

This isn't a problem on desktop. However, on mobile, it seems as if no matter what I do, when I upload an image, it's unworkably massive, zoomed in to the point of incoherency. I've tried using lower-resolution images, cropping them in Canva, cropping them in Squarespace, and all that happens is Squarespace zooms in further on the image, making it even more incomprehensible.

Squarespace desperately needs a "zoom" function for its images. (And the ability to delete files; my library is now clogged with all my unsuccessful attempts to upload an image that would fit.) But until then, does anyone know of a workaround? I'm willing to perform a code injection if necessary.

Thanks in advance,
Your pal,
LAVATORR