hello,
use the module class suffix nopadding
add this to the light.css file.nopadding .module-body {padding: 0;}
also there is a <p></p> element surrounding your image tag. remove that. the <p> element brings with it a top and bottom margin in this template.
If you are using the default editor "TinyMCE" replace it with RokPad or the JCE editor. TinyMCE is to editor plugins what IE is to browsers (only worse, imho). If you need a WYSIWYG editor install the JCE (Joomla Content Editor) extension and make it the default editor in your global configuration. If you do not need a WYSIWYG editor and would prefer just a good html editor install the RokPad extension by Rocket Theme. If you choose JCE you will see in the upper left of the editor the words Show/Hide click on that to switch between WYSIWYG and HTML editing.