Adding in image links when creating a theme in Magento requires a special snippet of code to ensure the path is correct.
When you need to add in an image in Magento you first need to make sure the image is in the correct theme folder. To do this you need to place the image file in /skin/frontend/default/your_theme_name/images
Now if you need to add a link to this image in the admin panel when using the CMS section for pages or static blocks you simply use the below code.
<img src="{{skin_url="images/your_file_name.jpg"}}" alt="alt text" />
This code will automatically put in the path to the theme you are currently using.
If you need to put an image link in an actual .phtml template file the same code can be used but it needs to be slightly modified to below.
<img src="<?php echo($this->getSkinUrl('images/your_file_name.jpg')) ?>" alt="at text" />