Some of our users having troubles with changing background of "about" section on some certain home-page variations. Here is short instruction.
Firstly, open page in edit mode and find this bock. On the right top corner of each section placed control buttons. One of them – settings button. Click on it.
You will see settings window. Switch tab to "Design options" and there you will be able to set background image and it's options(like background-size, default color or repeat-mode).