How to use an array of categories as a dropdown?

Try this,

$categories_array = array();
$categories = get_categories();
foreach( $categories as $category ){
  $categories_array[] = $category->term_id;
}

array(
  'param_name'    => 'category_id',
  'type'          => 'dropdown',
  'value'         => $categories_array, // here I'm stuck
  'heading'       => __('Category filter:', 'overmax'),
  'description'   => '',
  'holder'        => 'div',
  'class'         => ''
),