Alternate approach to removing custom image header upload in WP 3.0.

yoursite-image-header.php

<?php
/*
 * This approach is what Andrew Nacin suggested[1] instead of [2] and requested via email by Steve Wolfson.
 * Given it's complexity I can't advise te use of [1] and still recomment [2].  See also: [3][4].
 *
 * Author: Mike Schinkel (http://mikeschinkel.com)
 *
 * [1] http://lists.automattic.com/pipermail/wp-hackers/2010-November/036172.html
 * [2] http://lists.automattic.com/pipermail/wp-hackers/2010-November/036170.html
 * [3] https://gist.github.com/717514
 * [4] https://gist.github.com/717515
 * 
 */

require_once(ABSPATH . "wp-admin/custom-header.php");
class Yoursite_Image_Header extends Custom_Image_Header {
	function __construct($admin_header_callback,$admin_image_div_callback) {
		parent::__construct($admin_header_callback,$admin_image_div_callback);
	}
	static function on_load() {
		add_action('after_setup_theme',array(__CLASS__,'action_after_setup_theme'),11);
	}
	static function action_after_setup_theme() {
		$custom_image_header = $GLOBALS['custom_image_header'];
		remove_action('admin_menu', array(&$GLOBALS['custom_image_header'], 'init'));
		$GLOBALS['custom_image_header'] =& new Yoursite_Image_Header(
			$custom_image_header->admin_header_callback,
			$custom_image_header->admin_image_div_callback
		);
		add_action('admin_menu', array(&$GLOBALS['custom_image_header'], 'init'));
	}
	function step_1() {
		$this->process_default_headers();
?>

<div class="wrap">
<?php screen_icon(); ?>
<h2><?php _e('Custom Header'); ?></h2>

<?php if ( ! empty( $this->updated ) ) { ?>
<div id="message" class="updated">
<p><?php printf( __( 'Header updated. <a href="%s">Visit your site</a> to see how it looks.' ), home_url( '/' ) ); ?></p>
</div>
<?php } ?>

<h3><?php _e( 'Header Image' ) ?></h3>
<table class="form-table">
<tbody>


<tr valign="top">
<th scope="row"><?php _e( 'Preview' ); ?></th>
<td >
	<?php if ( $this->admin_image_div_callback ) {
	  call_user_func( $this->admin_image_div_callback );
	} else {
	?>
	<div id="headimg" style="max-width:<?php echo HEADER_IMAGE_WIDTH; ?>px;height:<?php echo HEADER_IMAGE_HEIGHT; ?>px;background-image:url(<?php esc_url ( header_image() ) ?>);">
		<?php
		if ( 'blank' == get_theme_mod('header_textcolor', HEADER_TEXTCOLOR) || '' == get_theme_mod('header_textcolor', HEADER_TEXTCOLOR) || ! $this->header_text() )
			$style = ' style="display:none;"';
		else
			$style = ' style="color:#' . get_theme_mod( 'header_textcolor', HEADER_TEXTCOLOR ) . ';"';
		?>
		<h1><a id="name"<?php echo $style; ?> onclick="return false;" href="<?php bloginfo('url'); ?>"><?php bloginfo( 'name' ); ?></a></h1>
		<div id="desc"<?php echo $style; ?>><?php bloginfo( 'description' ); ?></div>
	</div>
	<?php } ?>
</td>
</tr>

</tbody>
</table>

<form method="post" action="<?php echo esc_attr( add_query_arg( 'step', 1 ) ) ?>">
<table class="form-table">
<tbody>
	<?php if ( ! empty( $this->default_headers ) ) : ?>
<tr valign="top">
<th scope="row"><?php _e( 'Default Images' ); ?></th>
<td>
	<?php
		$this->show_default_header_selector();
	?>
</td>
</tr>
	<?php endif;

	if ( get_header_image() ) : ?>
<tr valign="top">
<th scope="row"><?php _e( 'Remove Image' ); ?></th>
<td>
	<p><?php _e( 'This will remove the header image. You will not be able to restore any customizations.' ) ?></p>
	<input type="submit" class="button" name="removeheader" value="<?php esc_attr_e( 'Remove Header Image' ); ?>" />
</td>
</tr>
	<?php endif;

	if ( defined( 'HEADER_IMAGE' ) ) : ?>
<tr valign="top">
<th scope="row"><?php _e( 'Reset Image' ); ?></th>
<td>
	<p><?php _e( 'This will restore the original header image. You will not be able to restore any customizations.' ) ?></p>
	<input type="submit" class="button" name="resetheader" value="<?php esc_attr_e( 'Restore Original Header Image' ); ?>" />
</td>
</tr>
	<?php endif; ?>
</tbody>
</table>

	<?php if ( $this->header_text() ) : ?>
<h3><?php _e( 'Header Text' ) ?></h3>
<table class="form-table">
<tbody>
<tr valign="top" class="hide-if-no-js">
<th scope="row"><?php _e( 'Display Text' ); ?></th>
<td>
	<p>
	<?php $hidetext = get_theme_mod( 'header_textcolor', HEADER_TEXTCOLOR ); ?>
	<label><input type="radio" value="1" name="hidetext" id="hidetext"<?php checked( ( 'blank' == $hidetext || empty( $hidetext ) )  ? true : false ); ?> /> <?php _e( 'No' ); ?></label>
	<label><input type="radio" value="0" name="hidetext" id="showtext"<?php checked( ( 'blank' == $hidetext || empty( $hidetext ) ) ? false : true ); ?> /> <?php _e( 'Yes' ); ?></label>
	</p>
</td>
</tr>

<tr valign="top" id="text-color-row">
<th scope="row"><?php _e( 'Text Color' ); ?></th>
<td>
	<p>
		<input type="text" name="text-color" id="text-color" value="#<?php echo esc_attr( get_theme_mod( 'header_textcolor', HEADER_TEXTCOLOR ) ); ?>" />
		<span class="description hide-if-js"><?php _e( 'If you want to hide header text, add <strong>#blank</strong> as text color.' );?></span>
		<input type="button" class="button hide-if-no-js" value="<?php esc_attr_e( 'Select a Color' ); ?>" id="pickcolor" />
	</p>
	<div id="color-picker" style="z-index: 100; background:#eee; border:1px solid #ccc; position:absolute; display:none;"></div>
</td>
</tr>

	<?php if ( defined('HEADER_TEXTCOLOR') && get_theme_mod('header_textcolor') ) { ?>
<tr valign="top">
<th scope="row"><?php _e('Reset Text Color'); ?></th>
<td>
	<p><?php _e( 'This will restore the original header text. You will not be able to restore any customizations.' ) ?></p>
	<input type="submit" class="button" name="resettext" value="<?php esc_attr_e( 'Restore Original Header Text' ); ?>" />
</td>
</tr>
	<?php } ?>

</tbody>
</table>
	<?php endif;

wp_nonce_field( 'custom-header-options', '_wpnonce-custom-header-options' ); ?>
<p class="submit"><input type="submit" class="button-primary" name="save-header-options" value="<?php esc_attr_e( 'Save Changes' ); ?>" /></p>
</form>
</div>

<?php
	}
}
Yoursite_Image_Header::on_load();