<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/08/25/changing-a-checkbox-controls-icon/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">
    
    <mx:Script>
        <![CDATA[
            [Bindable]
            [Embed(source="assets/icon_accept.gif")]
            public var AcceptIcon:Class;
            
            [Bindable]
            [Embed(source="assets/icon_alert.gif")]
            public var AlertIcon:Class;
        ]]>
    </mx:Script>

    <mx:CheckBox id="checkBox"
            label="Custom icon test (selected={checkBox.selected})"

            disabledIcon="{AlertIcon}"
            downIcon="{AlertIcon}"
            overIcon="{AlertIcon}"
            upIcon="{AlertIcon}"
            
            selectedDisabledIcon="{AcceptIcon}"
            selectedDownIcon="{AcceptIcon}"
            selectedOverIcon="{AcceptIcon}"
            selectedUpIcon="{AcceptIcon}"
         />
    
</mx:Application>