The upload of a picture for a custom header is not yet implemented, It will be available in 0.9 version soon this week.
By now, you can set a custom header by writing and activating a custom plugin. Here is an example how to do it. Copy this code in a php file, setting on it the URL to your image (in the #header line), and upload to your plugins folder. Activate it and it is done!
<?php
/*
Plugin Name: My Custom Header
Plugin URI: https://alkivia.org/chameleon
Description: Custom header for chameleon theme.
Version: 1.0
Author: Your name
Author URI: https://alkivia.org
*/
function my_theme_header ( $header ) {
return '';
}
add_filter('chameleon_header', 'my_theme_header');
function my_custom_header() {
echo "<style type='text/css'>
#header { background: url('https://alkivia.org/images/head.jpg'); }
</style>";
}
add_action('wp_head', 'my_custom_header');
?>
As said, uploading the image will be available in 0.9 version this week. Just consider the default image size is 970×120 pixels.
Sorry for the inconvenience to have to do it that way by now.