Customizing "First Run Wizard": embedding picture

Hi, iam Customizing the “first run wizard” by editing the wizard.php.

It Looks like this:

<p align="center">
<img src="/sourcesomewhere/…/logo.png" width="300">

<br><br>
<font size="+1">

Herzlich Willkommen ...<br> 

My Question: the Picture can not be displayed, someone having a tipp?

Greetings

Edit: Permissions are set