You can adjust some code to make that work properly...in the css...both the style.css and ie.css (dealing with body background image)...and also /ndxz-studio/site/plugin/index.php...change line 210 from...
$style .= ($img != '') ? "\nbackground-image: url(".BASEURL."/files/$img);\nbackground-repeat: $tile;\nbackground-position: 215px 0;\nbackground-attachment: fixed;\n" : '';
to...
$style .= ($img != '') ? "\nbackground-image: url(".BASEURL."/files/$img);\nbackground-repeat: $tile;\nbackground-position: 0 0;\nbackground-attachment: fixed;\n" : '';
Should make the image left justified in every situation for you.