I checked the theme and looks like I set the default of background-size property to cover in the code in framework/extensions/stylizer.php file (line number 76). Actually I need one extra option in the page edit or post edit window for setting the background size as well – cover, contain, auto so that I do not set the default value. For now, you can insert the following CSS into Custom CSS tab in the theme options –
#before-content-area-wrap { background-size: auto; }
The disadvantage is that this defaults the value to background-size:auto for all posts/pages. Hence, it is better to have something prefixed with page id or post id as
.page-id-484 #before-content-area-wrap { background-size: auto; }
or
.postid-3490 #before-content-area-wrap { background-size: auto; }
depending on whether you are doing this for post or a page. Hope this helps. Let me know if you still have trouble.