functions.php

function check_small_image() {
	/**
	 * Get our meta value for the image
	 * We use get_the_ID() to get the currently used loop post
	 */
    $small_image = get_post_meta( get_the_ID(), 'small-image-meta', true );

	/**
	 * Check if there was actualy an image stored
	 */
    if ( $small_image ) {
    	/**
    	 * An image was found, we use the printf() function to 
    	 * output and sanitize our values to avoid exploits and such
    	 */
    	printf(
    		'<img src="%s" alt="%s" />',
    		esc_url( $small_image ),
    		__( 'Alternative text', 'textdomain' )
		);
    }
    else {
        echo 'Hello';
    }
}