The fact that the graphic is within an <a> tag should have no bearing on it's showing or not. Check the path to the graphic in the source code or by displaying the properties.
This, to be blunt, is an HTML question and has nothing to do with PHP. The fact that you use PHP to create (obviously) invalid HTML or you fill in a bad path is merely circumstancial.
Foloow Forri's advice and post the code.