Index: /CKEditor/trunk/_source/plugins/button/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/button/plugin.js	(revision 3185)
+++ /CKEditor/trunk/_source/plugins/button/plugin.js	(revision 3186)
@@ -57,4 +57,6 @@
 
 	this.className = definition.className || ( definition.command && 'cke_button_' + definition.command ) || '';
+
+	this.icon = definition.icon;
 
 	/**
@@ -176,5 +178,11 @@
 				' onfocus="return CKEDITOR.ui.button._.focus(', index, ', event);"' +
 				' onclick="return CKEDITOR.ui.button._.click(', index, ', event);">' +
-					'<span class="cke_icon"></span>' +
+					'<span class="cke_icon"' );
+
+		if ( this.icon )
+			output.push( ' style="background-image:url(', CKEDITOR.getUrl( this.icon ), ');background-position:0 0;"' );
+
+		output.push(
+					'></span>' +
 					'<span class="cke_label">', this.label, '</span>' +
 			'</a>' );