Why can't I use background image and color together?

Question

What I am trying to do is to show both background-color and background-image, so that half of my div will cover the right shadow backg

Answer 1

Make half of the image transparent so the background colour is seen through it.

Else simply add another div taking up 50% up the container div and float it either left or right. Then apply either the image or the colour to it.