If you need to add some custom CSS or JS to the Design Options admin page, you can use the init_design_admin() method to enqueue your scripts.

To illustrate, let’s say you have a CSS file named custom_design_admin.css, a JS file named custom_design_admin.js, and you’ve placed both of these files in your Skin folder. Here’s how your init_design_admin() method would look:

public function init_design_admin() {
	wp_enqueue_style('custom-design-admin', THESIS_SKIN_URL. '/custom_design_admin.css');
	wp_enqueue_script('custom-design-admin', THESIS_SKIN_URL. '/custom_design_admin.js');