Theme Review: post thumbnail, header image, content width

RECOMMENDED: No reference to the_post_thumbnail() was found in the theme. It is recommended that the theme implement this functionality instead of using custom fields for thumbnails.

This is because you are not using the_post_thumbnail() in your theme, you are trying to get an image from the post content. This means there is no way for a user to explicitly set which image is shown wherever you are using retImage(). I would include the ability for retImage() to try use the thumbnail, something like:

// thumbnail list 
function retImage($content) {

    if( has_post_thumbnail() )
         return the_post_thumbnail( 'thumbnail' ); 

    $pattern="/<img.*?src=[\'|\"](.*?(?:[\.gif|\.jpg]))[\'|\"].*?[\/]?>/";
    preg_match_all($pattern,$content,$match); 
    if(empty($match[0][0])){
             echo "<img src=\"";
             bloginfo('template_url');
             echo "/images/thumbnail.png\" />";
    } else {

        echo  $match[0][0];
    }
}

You may also need to include add_theme_support( 'post-thumbnails' ) in your functions.php

RECOMMENDED: No reference to add_custom_image_header was found in the theme. It is recommended that the theme implement this functionality if using an image for the header.

If you theme has a header image, it is recommended to use the WordPress header image API, you can find out more about it here: http://codex.wordpress.org/Function_Reference/add_custom_image_header

This would enable the user to change the header image via the admin (Appearance -> Custom Header) or something alike.

Embedded videos overlap sidebar. Please set the content_width variable
The $content_width should be a global variable:

global $content_width;
$content_width = 960;