Index: src/wp-admin/css/customize-controls.css
===================================================================
--- src/wp-admin/css/customize-controls.css	(revision 32330)
+++ src/wp-admin/css/customize-controls.css	(working copy)
@@ -764,31 +764,24 @@
 /* Header control: overlay "close" button */
 
 .customize-control-header .uploaded .header-view .close {
-	font-size: 2em;
-	color: grey;
+	font-size: 20px;
+	color: #fff;
+	background: #555;
+	background: rgba(0, 0, 0, 0.5);
 	position: absolute;
-	visibility: hidden;
 	top: 10px;
-	right: 10px;
+	right: -999px;
 	z-index: 1;
-	width: 20px;
-	height: 20px;
+	width: 26px;
+	height: 26px;
 	cursor: pointer;
 }
 
-.customize-control-header .uploaded .header-view .close:hover {
- color: black;
- text-shadow:
-    -1px -1px 0 #fff,
-    1px -1px 0 #fff,
-    -1px 1px 0 #fff,
-    1px 1px 0 #fff;
+.customize-control-header .header-view:hover .close,
+.customize-control-header .header-view .close:focus {
+	right: 10px;
 }
 
-.customize-control-header .header-view:hover .close {
-	visibility: visible;
-}
-
 /* Header control: randomiz(s)er */
 
 .customize-control-header .random.placeholder {
Index: src/wp-includes/class-wp-customize-control.php
===================================================================
--- src/wp-includes/class-wp-customize-control.php	(revision 32330)
+++ src/wp-includes/class-wp-customize-control.php	(working copy)
@@ -1074,7 +1074,7 @@
 			<# } else { #>
 
 			<# if (data.type === 'uploaded') { #>
-				<div class="dashicons dashicons-no close"></div>
+				<button type="button" class="dashicons dashicons-no close"><span class="screen-reader-text"><?php _e( 'Remove image' ); ?></span></button>
 			<# } #>
 
 			<button type="button" class="choice thumbnail"