outputting image from custom module
For outputing image, you should use theme function, with image theming. And path argument inside.

For example:

$img = theme('image', array('path' =&gt; "path to image"));
// $img will containt the image tag.
// path can be relative from drupal root, or it can be 'files' path (public://image.jpg)


Read more about it, you can here: https://api.drupal.org/api/drupal/includes%21theme.inc/function/theme_image/7

The power of Drupal in overwriting, so I suggest you to use theme way.