Order Summary Component using Flexbox

This design looks simple but took must of my time. I have a few questions that I need help on.

1. How do you get the background with both image and color using background shortcut?
2. How do you prevent the background image from shrinking when you reduce the width of the screen? NB: Try minimizing my design on a large screen.
3. What is the best practice for handling decorative image like the illustration in this challenge? Do you set it as background or as image like I did?

All feedback to make my code simpler will be appreciated.

Thanks