整理钢笔背景图到样式表中，js调用css来实现背景图片加载

Bootstrap.Admin/Content/css/site.css

@@ -548,7 +548,6 @@ ul.breadcrumb {
     bottom: 40px;
     right: 0;
     top: 94px;
-    background-image: url('../images/bg.jpg');
     overflow: hidden;
 }
 
@@ -557,3 +556,8 @@ ul.breadcrumb {
         height: 100%;
         border: none;
     }
+
+.welcome-bg {
+    background-image: url('../images/bg.jpg');
+    background-size: 100% 100%;
+}

Bootstrap.Admin/Scripts/well.js

@@ -1,5 +1,5 @@
 $(function () {
-    $('#main-content').css('backgroundImage', 'url("../content/images/bg.jpg")');
+    $('#main-content').addClass('welcome-bg');
     function resposive() {
         var height = $(window).height();
         if (height > 672)

Bootstrap.Admin/Views/Home/Index.cshtml

@@ -9,5 +9,5 @@
 @section header {
     @Html.Partial("Header", Model)
 }
-<div id="content" class="content-body">
+<div id="content" class="content-body welcome-bg">
 </div>