What you are asking for is not that easy.

You can use link events inside a dynamic textfield. That way a link event is dispatched when you click the link but it doesn't work for hovering.

What might work is using getCharIndexAtPoint(x, y) with the mouse coordinates to get the index of the character below the mouse pointer, use getTextFormat(beginIndex, endIndex) with that index value to get the text format of that character and use the url property of that text format to detect what the link is. When you have the link, you can use it to load the image.