Need custom picture field for pages

It sounds like “Featured” or “Thumbnail” images would work. These are enabled by default for ‘posts’. For ‘pages’ they need to be enabled, but that is as simple as adding add_post_type_support( 'page', 'thumbnail' ); to your theme’s functions.php hooked on init, and, of course, modifying the theme template files to display the featured image.

function add_featured_to_post_wpse_83508() {
  add_post_type_support( 'page', 'thumbnail' );
}
add_action('init','add_featured_to_post_wpse_83508');

The theme itself has to register its support with add_theme_support( 'post-thumbnails' );

In the Loop, the_post_thumbnail() will display the image