I did some digging but personally I do not have the environment to test it out. So you might need to check it for yourself.
Can you please try the below:
.header-task{
background-image: url("static(image/nightlandscape.jpg"));
background-repeat: no-repeat;
background-size: 100% 200%;
height: 120px;
position: relative;
}
If your STATIC_URL is '/static/' (I believe that is in settings.py), this will be rendered as:
.header-task{
background-image: url("/static/image/nightlandscape.jpg");
background-repeat: no-repeat;
background-size: 100% 200%;
height: 120px;
position: relative;
}
Another possibility:
.header-task{
background-image: url('{% static 'nightlandscape.jpg' %}') or url('{% static "/img/nightlandscape.jpg" %}')
background-repeat: no-repeat;
background-size: 100% 200%;
height: 120px;
position: relative;
}
but for that I think you would need to load static files first: {% load static%} in your HTML and then load the stylesheet.
<head>
<style>
{% include "path/to/my_styles.css" %}
</style>
</head>
Possibly simply changing url("..\image\nightlandscape.jpg") to url("../image/nightlandscape.jpg")