Responsive, mobile first, using Sass and Vanilla JS

Any feedback would be welcome! I initially included the illustration in img tags, then changed my mind and included them in css as background images, not sure which approach is better in this situation.

Also: can someone suggest why images are not showing up in the screenshot? I've included them in my repo, and I can see them when I open the deployed page in Vercel, not sure what's gone wrong between here and there! Thanks :)