replace your my-first-custom-element.php with code below.

gistfile1.txt

replace your my-first-custom-element.php with code below.

my-first-custom-element

<?php
/*
Element Description: VC Info Box
*/
// Element Class 
class vcInfoBox extends WPBakeryShortCode {
	//Element Init
	function __construct(){
		add_action( 'init', array( $this, 'vc_infobox_mapping' ) );
		add_shortcode( 'vc_infobox', array( $this, 'vc_infobox_html' ) );
	}

	//Element Mapping
	public function vc_infobox_mapping(){
		//stop all if VC is not enabled
		if ( !defined( 'WPB_VC_VERSION' ) ){
			return;
		}
		// Map the block of VC_map
		vc_map(
			array(
				'name' => __('VC_INFOBOX', 'text-domain'),
				'base' => 'vc_infobox',
				'description' => __('Infobox custom element', 'textdomain'),
				'category'	=> __('Custom Element', 'text-domain'), //to create custom tab "Custom element"
				//'icon'	=> get_template_directory().'/vc-extend/puzzle.png',
				'icon' => 'Textbox',
				'params' => array(
					array(
						'type'=>'textfield',
						'holder' => 'h3',
						'class' => 'title-class',
						'heading'	=> __('Title', 'text-domain'),
						'param_name' => 'title',
						'value' => __( 'Default value', 'text-domain'),
						'description' => __('Box Title', 'text-domain'),
						'admin_level' => false,
						'weight' => 0,
						'group' => 'custom group',
						),
					array(
						'type' => 'textarea',
						'holder'=> 'div',
						'class' => 'text-class',
						'heading' => __('Text', 'text-domain'),
						'param_name' => 'text',
						'value' => __( 'Default Value', 'text-domain'),
						'description' => __('Box Text', 'text-domain'),
						'admin_level' => false,
						'wight' => 0,
						'group' => 'custom group',
						),
					array(
						'type' => 'attach_image',
						'holder'=> 'div',
						'class' => '',
						'heading' => __('Thumbnail', 'text-domain'),
						'param_name' => 'image',
						'value' => __( 'Default Value', 'text-domain'),
						'description' => __('Box Image', 'text-domain'),
						'admin_level' => false,
						'wight' => 0,
						'group' => 'custom group',
						),
					array(
						'type' => 'vc_link',
						'holder'=> 'div',
						'class' => '',
						'heading' => __('Link', 'text-domain'),
						'param_name' => 'link',
						'value' => __( 'Default Value', 'text-domain'),
						'description' => __('Box Link', 'text-domain'),
						'admin_level' => false,
						'wight' => 0,
						'group' => 'custom group',
						),
					array(
						'type' => 'dropdown',
						'holder'=> 'div',
						'class' => '',
						'heading' => __('Dropdown', 'text-domain'),
						'param_name' => 'dropdown',
						  'value' => array(
								    __( 'Ram',  "my-text-domain"  ) => 'option1value',
								    __( 'Shyam',  "my-text-domain"  ) => 'option2value',
								    __( 'Gita',  "my-text-domain"  ) => 'option3value',
							  ),
						'description' => __('Box Dropdown', 'text-domain'),
						'admin_level' => false,
						'wight' => 0,
						'group' => 'custom group',
						),					
					) 
				)
			);

	}

	//Element HTML
	public function vc_infobox_html($atts){
		//params extraction
		extract(
			shortcode_atts(
				array(
					'title' => '',
					'text' => '',
					'image' => '',
					'link' => '',
					'dropdown' => '',

					),
				$atts
				)
			);

		//Fill $html var with data
		$html='
		<div class="vc-infobox-wrap">
			<h2 class="vc-infobox-title">' . $title . '</h2>
			<div class="vc-infobox-text">' . $text . '</div>
			<div class="vc-infobox-link">' . $link . '</div>
			
		</div>
		'
		
		;
		return $html;
	}
}//End element class

new vcInfoBox();
?>
<div><img src=""> </div>