iconContentLoader is really just BitmapImage's contentLoader property. Check out http://help.adobe.com/en_US/FlashPlatform/beta/reference/actionscript/3/spark/primitives/B itmapImage.html and https://opensource.adobe.com/wiki/display/flexsdk/Spark+Image?showComments=false for some info on that property.
I'm not sure you need it for what you're trying to do. contentLoader is really for caching content or queueing up loads in a certain way (most useful when making network requests). If you're just trying to associate some data item with BitmapData, then try using iconFunction.
Hope that helps,