css_background is a django-cms plugin which allow you to edit css background image or color from the edit mode
you can define your template like this:
{% load placeholder_tags placeholder_attr %}
<div style="{% placeholder_attr 'My Background Css Placeholder' 'CssBackground' 'css_background' %}">
{% placeholder 'My Background Css Placeholder' %}
</div>after that set the provide a CSS Background plugin for this placeholder, and chose an image, or set rgb or rgba for a colored background