How to add default images for custom backgrounds?

The custom header feature allows (in some code I have found) to suggest several default images to use in the custom header.

Could the same be built in the custom background?

The idea is to have already some textures available for the user to choose from in the theme.

Any ideas?

if you are asking default background image for
add_theme_support( 'custom-background'); then it can be set using 'default-image' => get_template_directory_uri() . '/images/pattern.png',

complete code will look like below.

$args = array(
'default-color'  => 'f0f0f0',
'default-repeat' => 'fixed',
'default-image'  => get_template_directory_uri() . '/assets/images/pattern.png',
);
add_theme_support( 'custom-background', $args );