Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 15790)
+++ wp-includes/media.php	(working copy)
@@ -839,7 +839,7 @@
 			}
 		</style>
 		<!-- see gallery_shortcode() in wp-includes/media.php -->
-		<div id='$selector' class='gallery galleryid-{$id}'>");
+		<div id='$selector' class='gallery galleryid-{$id} gallery-columns-{$columns} gallery-size-{$size}'>");
 
 	$i = 0;
 	foreach ( $attachments as $id => $attachment ) {
Index: wp-content/themes/twentyten/style.css
===================================================================
--- wp-content/themes/twentyten/style.css	(revision 15790)
+++ wp-content/themes/twentyten/style.css	(working copy)
@@ -829,9 +829,23 @@
 	text-align: center;
 	width: 33%;
 }
+.gallery-columns-2 .gallery-item {
+	width: 50%;
+}
+.gallery-columns-4 .gallery-item {
+	width: 25%;
+}
 .gallery img {
 	border: 2px solid #cfcfcf;
 }
+.gallery-columns-2 .attachment-medium {
+	max-width: 92%;
+	height: auto;
+}
+.gallery-columns-4 .attachment-thumbnail {
+	max-width: 84%;
+	height: auto;
+}
 .gallery .gallery-caption {
 	color: #888;
 	font-size: 12px;