Add icon on spark button skin

Question

Hello all I am trying to add different icon on different buttons. I have my skin file ready but not sure if I have to create different skin class for different button. It sounds inefficient. Any suggestions? Thanks for the reply...
<s:Button id="pass"
      width="110"
      height="35"
      fontWeight="bold"
          fontSize="12"
      fontFamily="arial"
      label="Past Track"
     click="pass_clickHandler(event)" skinClass="skins.CustomSkin"/>      
<s:Button id="future"
      width="110"
      height="20"
      fontWeight="bold"
      fontSize="12"
      fontFamily="arial"
      label="Future Plan"
          click="future_clickHandler(event)"
          skinClass="skins.CustomSkin"/>
Skin.....
   <!-- layer 2: fill -->
    <!--- @private -->
    <s:Rect id="fill" left="1" right="1" top="1" bottom="1" radiusX="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="#304fd7"
                             color.over="#4b6bf6"
                             color.down="0xAAAAAA"
                             alpha="0.85" />
            <s:GradientEntry color="#1f38a3"
                             color.over="#3653cf"
                             color.down="0x929496"
                             alpha="0.85" />
        </s:LinearGradient>
    </s:fill>
</s:Rect>
<!-- icon --> // I could add my icon here but that would make me to create 
                  //different icon image for different button

Answer 1

so you could do something like this even though it doesn't have to be a required item.
    public class ImageButton extends Button
         *  The skin part that defines the area where
         *  the user may drag to resize the window.
        [SkinPart(required="true")]
        public var buttonImage:Object
Then , in your skin you would have an mxml image with the same name ( buttonImage ) that you would position in the skin.  In the mxml where you use the class you could just do
<custom:ImageButton id="ib" buttonImage="assets/myButton.jpg" />
I must warn you though , skinning is not my specialty.
If this post was helpful please mark it as such.
Sincerely ,
  Ubu