Well, I made a topic earlier on the same subject, the content appeared but the image does not appear.
Follow the code:
<!--PARA ACEITAR ACENTOS-->
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<!--CONTEÚDO EM PORTUGUÊS-->
<meta property="og:locale" content="pt_BR">
<!--URL DO SITE-->
<meta property="og:url" content="http://www.meudomínio.com/index.php">
<!--TÍTULO E NOME DO SITE-->
<meta property="og:title" content="TítuloSite">
<meta property="og:site_name" content="Nome do site">
<!-- DESCRIÇÃO DO SITE-->
<meta property="og:description" content="descrição site.">
<!-- IMAGEM DO SITE -->
<meta property="og:image" content="images/intro.jpg"/>
<meta property="og:image:type" content="image/jpeg">
<meta property="og:image:width" content="800">
<meta property="og:image:height" content="600">
Note: I checked the extension, I have doubt of a detail. The image is pretty big ... and it's all in the head.