"Theme Customizer" - different background image for different category - background-image

Question

I'm trying to make setting in theme customizer which will allow me to choose different background image to different category. I have two settings working separately, but i don't know how to combine them to work together and it seems like there was no problem like this before.
In theme customizer it looks like
> this <.
How make it work together?
EDIT:
I was trying in many ways to acomplish this, but only thing that worked as i wanted was creating a section for each category and add background image there, like this:
$wp_customize->add_section( 'background_section_cat_a', array(
'title' => __( 'Category: cat_a', 'twentythirteen-child'),
'description' => 'Options prepared to change background settings', 'twentythirteen-child',
'priority' => 160,
'panel' => 'background_panel',
));
$wp_customize->add_setting( 'background_image_cat_a', array(
'default' => 'abc.jpg',
));
$wp_customize->add_control( new WP_Customize_Image_Control( $wp_customize, 'background_image_cat_a', array(
'label' => __( 'Select background image', 'twentythirteen-child' ),
'section' => 'background_section_cat_a',
'settings' => 'background_image_cat_a',
)));
and use this setting:
body.category-cat-a {
background-image: url(<?php echo get_theme_mod('background_image_cat_a'); ?>);}
But when I add new category, I have to enter my theme customizer options and add it there, and it is very time time consuming.

Answer 1

There is another way:
1. Add custom field with image to your Category taxonomy
2. call your image in category.php page.