Generating images from an array of categories

is_category() takes an array as arguments if you want to check for more than one category. But you can make it even easier with a check for existing files:

if ( is_category() )
{
    $slug       = get_queried_object()->slug;
    $theme_path = "/images/slider_$slug.png";
    $file       = get_template_directory() . $theme_path;

    if ( file_exists( $file ) )
    {
        echo '<img src="' 
            . get_template_directory_uri() . $theme_path 
            . '" alt="" height="200px" width="960px" />';
    }
}