Consistently style image in blob and diff

app/assets/stylesheets/framework/files.scss

@@ -66,10 +66,10 @@
     &.video {
       background: $file-image-bg;
       text-align: center;
+      padding: 30px;
 
       img,
       video {
-        padding: 20px;
         max-width: 80%;
       }
     }

app/assets/stylesheets/framework/variables.scss

@@ -247,7 +247,6 @@ $dark-diff-match-bg: rgba(255, 255, 255, 0.3);
 $dark-diff-match-color: rgba(255, 255, 255, 0.1);
 $file-mode-changed: #777;
 $file-mode-changed: #777;
-$diff-image-bg: #ddd;
 $diff-image-info-color: grey;
 $diff-swipe-border: #999;
 $diff-view-modes-color: grey;

app/assets/stylesheets/pages/diff.scss

@@ -158,7 +158,7 @@
   }
 
   .image {
-    background: $diff-image-bg;
+    background: $file-image-bg;
     text-align: center;
     padding: 30px;