Embedding images in a block from url
For any source or path of any thing in drupal site use src like this. It will work everywhere.

&lt;?php $src = base_path() .'sites/files/logo.png'; ?&gt;


This src use like

&lt;img alt="logo" src=" &lt;?php echo $src ; ?&gt;"&gt;


Enable PHP filter module that come with core module.

and in Block Body Choose Text format as PHP CODE.

I assuming block is created using Block module(Block UI)