Create a module that add text/image to a specific type nodes
Various ways of doing this. Either edit your tpl file. Create a node--article.tpl.php in your theme folder (copy the syntax from node.tpl.php) and modify the code to add your desired label. If you need to print username then the global $user is available. Just define it as global and access username as $user-&gt;name. 

Or you could use Panels module. It's very flexible and powerful. 

For creating custom module to do this, there are various approaches. One good way is this: 

In your custom mymodule.module file, use the hook_node_view like this:

function mymodule_node_view($node, $view_mode) {
    if ($node-&gt;type=="article"){
        if ($view_mode == 'full'){
            $node-&gt;content['my_extra_content'] = array(
                 "#markup"=&gt; '&lt;strong&gt;Made by me!&lt;/strong&gt;',
                 "#weight"=&gt; 100
              );  
           }
         return $node;
   }   
}


After this, Made by me should appear at the bottom of each node. If you want it to appear at the top, then just modify the weight and give it some negative value.