here are some resources on theming.
Adding background support to twentythirteen
- Change the reference near line 525 in functions.php to “get_stylesheet_directory_uri()” to call the child theme’s customizer script.
- Copy the section on backgrounds from line 39-63 of twentytwelve/js/theme-customizer.js into the bottom of twentythirteen-child/js/theme-customizer.js
- Copy the theme support code from line 66-72 of twentytwelve/functions.php into the setup function of twentythirteen-child/functions.php near line 105
- Copy the section on backgrounds from line 416-447 of twentytwelve/functions.php into the body_class function of twentythirteen-child/functions.php near line 480
NOTE: Customizing settings from the back end will override the stylesheet definitions. To return to the stylesheet settings, click “Remove Header Image” to do exactly that, and to remove the background color, click into the hex entry field and hit backspace, then “Save and Publish”.